Compositions and methods for cardiac tissue repair

ABSTRACT

The invention features compositions comprising agents having cardiac protective activity isolated from epicardial progenitor cells and derivatives thereof, and methods for the use of such compositions.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation-in-part of International ApplicationNo. PCT/US2010/001540, which was filed on May 26, 2010, and published asInternational Publication No. WO 2010/138180, which claims the benefitof U.S. Provisional Application No. 61/181,071, which was filed on May26, 2009, the disclosures of which are hereby incorporated in theirentireties.

STATEMENT OF RIGHTS TO INVENTIONS MADE UNDER FEDERALLY SPONSOREDRESEARCH

This work was supported by the following grant from the NationalInstitutes of Health, Grant No: HL085210-02. The government has certainrights in the invention.

SEQUENCE LISTING

The instant application contains a Sequence Listing which has beensubmitted in ASCII format via EFS-Web and is hereby incorporated byreference in its entirety. Said ASCII copy, created on Oct. 26, 2011, isnamed 83811CIP.txt and is 49,195 bytes in size.

BACKGROUND OF THE INVENTION

Mammalian cells require a consistent source of oxygen and nutrients toallow them to function normally. When their access to oxygen andnutrients is interrupted, cell damage and death can quickly result.Certain cell types, including muscle cells and neurons are particularlyvulnerable to ischemic injury in connection with myocardial infarctionand stroke. Despite recent advances in treating ischemic injuries,stroke and myocardial infarction continue to kill or disable vastnumbers of people each year. In the United States alone, 600,000 newmyocardial infarctions and 320,000 recurrent attacks occur annually.About 38 percent of the people who experience a myocardial infarction ina given year will die, while many of those who survive will experiencesome loss in cardiac function. Current cell replacement strategies fortreating myocardial infarction involving the injection ofstem/progenitor cells result in modest improvements in cardiac function,at best. Low levels of engraftment, survival, and cell replacement afterinjection of adult or embryonic stem cells into the injured leftventricle wall are current issues that reduce the potentialeffectiveness of cell replacement strategies after myocardialinfarction. Moreover, infusion of cultured adult stem/progenitor cellscan be accompanied by microembolism and cardiac arrhythmias.Accordingly, improved methods of treating tissue injury, particularlyischemic injuries associated with myocardial infarction, are urgentlyrequired.

SUMMARY OF THE INVENTION

As described below, the present invention features compositions andmethods for treating or preventing cardiac tissue damage, includingdamage associated with an ischemic event.

In one aspect, the invention provides a pharmaceutical compositioncontaining or consisting essentially of one or more cellular factors(e.g., HGF, VEGF, SDF-1 alpha, and/or IGF-1) having cardiac protectiveactivity in a pharmaceutically acceptable excipient, where the cellularfactor is isolated from a cultured epicardial progenitor cell. In oneembodiment, the pharmaceutical composition comprises one or morecellular factors isolated from a cultured epicardial progenitor cell,and one or more recombinant cellular factors (e.g., HGF, VEGF, SDF-1alpha, and/or IGF-1).

In another aspect, the invention provides a pharmaceutical compositioncontaining a secreted cellular factor (e.g., HGF, VEGF, SDF-1 alpha,and/or IGF-1) in a pharmaceutically acceptable excipient, where thecellular factor is isolated from an epicardial progenitor cell selectedfor expression of epicardin, Nkx 2.5, Isl-1, GATA 5, WT1, Tbx18, and/orTbx5 polypeptides or polynucleotides; has a biological activity that isany one or more of reducing cell death in a cell population at riskthereof, increasing cell survival, reducing inflammation, increasingepicardial cell proliferation, increasing epithelial to mesenchymaltransformation, and increasing cardiac function; has a molecular weightthat is at least about 5 kD; and is inactivated by heat denaturation. Inone embodiment, the pharmaceutical composition comprises one or morecellular factors isolated from a cultured epicardial progenitor cell,and one or more recombinant cellular factors (e.g., HGF, VEGF, SDF-1alpha, and/or IGF-1).

In another aspect, the invention provides a method for producing apharmaceutical composition containing one or more cellular factors(e.g., HGF, VEGF, SDF-1 alpha, and/or IGF-1), the method involvingselecting an isolated epicardial progenitor cell that expresses any oneor more of epicardin, Nkx 2.5, Isl-1, GATA 5, WT1, Tbx18, and Tbx5polypeptides or polynucleotides; and isolating a composition comprisingone or more cellular factors from the cell, thereby generating acomposition that promotes cardiac tissue repair. In one embodiment, themethod involves identifying one or more of said cellular factors. Onceidentified, the cellular factors may be recombinantly expressed andadded to the pharmaceutical composition to increase the concentration ofsuch factors present in the composition.

In still another aspect, the invention provides a method for reducingcardiac cell death or increasing cardiac cell survival or proliferation,the method involving contacting a cardiac cell at risk of cell deathwith a composition comprising or consisting essentially of one or moresecreted cellular factors (e.g., HGF, VEGF, SDF-1 alpha, and/or IGF-1)having cardiac protective activity, where the factor is isolated from anepicardial progenitor cell in vitro. In one embodiment, thepharmaceutical composition comprises one or more cellular factorsisolated from a cultured epicardial progenitor cell, and one or morerecombinant cellular factors (e.g., HGF, VEGF, SDF-1 alpha, and/orIGF-1).

In yet another aspect, the invention provides a method for stabilizingor reducing cardiac tissue damage in a subject (e.g., a human orrodent), the method involving contacting a cardiac cell of the subjectwith a composition comprising one or more secreted cellular factors(e.g., HGF, VEGF, SDF-1 alpha, and/or IGF-1) having epicardialprotective activity, thereby stabilizing or reducing cardiac tissuedamage in the subject. In one embodiment, one or more of said cellularfactors are recombinantly expressed.

In another aspect, the invention provides a method for increasingcardiac function in a subject at risk of ischemic cardiac tissue damage,the method involving contacting a cardiac cell of the subject with oneor more secreted cellular factors (e.g., HGF, VEGF, SDF-1 alpha, and/orIGF-1) having epicardial protective activity, thereby increasing cardiacfunction in the subject. In one embodiment, one or more of said cellularfactors are recombinantly expressed.

In yet another aspect, the invention provides a method for treating orpreventing vascular rhexis in a subject (e.g., a human or rodent), themethod involving contacting a cardiac cell of the subject with acomposition comprising one or more secreted cellular factors (e.g., HGF,VEGF, SDF-1 alpha, and/or IGF-1) having epicardial protective activity,thereby treating or preventing vascular rhexis in the subject. In oneembodiment, one or more of said cellular factors are recombinantlyexpressed.

In still another aspect, the invention provides a method for reducingcardiac cell death or increasing cardiac cell survival or proliferation,the method involving contacting a cardiac cell at risk of cell death(e.g., apoptotic, necrotic) with an effective amount of a compositioncontaining one or more secreted cellular factors (e.g., HGF, VEGF, SDF-1alpha, and/or IGF-1) isolated from an epicardial progenitor cell thatexpresses any one or more of epicardin, Nkx 2.5, Isl-1, GATA 5, WT1,Tbx18, and Tbx5; thereby increasing cardiac cell survival orproliferation. In one embodiment, one or more of said cellular factorsare recombinantly expressed.

In another aspect, the invention provides a method for stabilizing orreducing cardiac tissue damage in a subject at risk thereof, the methodinvolving contacting a cardiac cell of the subject with an effectiveamount of a composition containing one or more secreted cellular factors(e.g., HGF, VEGF, SDF-1 alpha, and/or IGF-1) isolated from an epicardialprogenitor cell that expresses epicardin, Nkx 2.5, Isl-1, GATA 5, WT1,Tbx18, and Tbx5, thereby stabilizing or reducing cardiac tissue or heartdamage. In one embodiment, one or more of said cellular factors arerecombinantly expressed.

In yet another aspect, the invention provides a method for increasingcardiac function in a subject at risk of ischemic tissue damage, themethod involving contacting a cardiac cell of the subject with aneffective amount of a composition containing one or more secretedcellular factors (e.g., HGF, VEGF, SDF-1 alpha, and/or IGF-1) isolatedfrom an epicardial progenitor cell that expresses any one or more ofepicardin, Nkx 2.5, Isl-1, GATA 5, WT1, Tbx18, and Tbx5, therebyincreasing cardiac function. In one embodiment, one or more of saidcellular factors are recombinantly expressed.

In another aspect, the invention provides a method for treating orpreventing vascular rhexis in a subject, the method involving contactinga cardiac cell of the subject with an effective amount of a compositioncontaining one or more secreted cellular factors (e.g., HGF, VEGF, SDF-1alpha, and/or IGF-1) isolated from an epicardial progenitor cell thatexpresses epicardin, Nkx 2.5, Isl-1, GATA 5, WT1, Tbx18, and Tbx5,thereby treating or preventing vascular rhexis in the subject.

In still another aspect, the invention provides a method for identifyingan agent useful for cardiac tissue repair or regeneration, the methodinvolving contacting a cardiac cell at risk of cell death with acomposition containing a secreted cellular factor isolated from anepicardial progenitor cell selected for expression of any one or more ofepicardin, Nkx 2.5, Isl-1, GATA 5, WT1, Tbx18, and Tbx5; detecting anincrease in cell survival, growth, or proliferation or a decrease incell death relative to an untreated control cell; and isolating theagent, thereby identifying an agent useful for cardiac tissue repair orregeneration. In one embodiment, the method further involves purifyingthe factor. In other embodiments, the purification involves selectingfractions having a desired biological activity. In still otherembodiments, the selected fraction increases cardiac cell survival,reduces cardiac cell death, increases cardiac cell proliferation, orincreases cardiac tissue or heart function.

In another aspect, the invention provides a cellular compositioncontaining an isolated epicardial progenitor cell or progeny cellthereof that expresses any one or more of epicardin, Nkx 2.5, Isl-1,GATA 5, WT1, Tbx18, and Tbx5. In various embodiments, at least about 50%(60%, 70%, 80%, 90%, 95%, or 100%) of the cells present in thecomposition express any one or more of epicardin, Nkx 2.5, Isl-1, GATA5, WT1, Tbx18, and Tbx5 polypeptides or polynucleotides or are derivedfrom a progenitor cell that expresses any one or more of epicardin, Nkx2.5, Isl-1, GATA 5, WT1, Tbx18, and Tbx5 polypeptides orpolynucleotides. In various embodiments, the cellular compositioncontains cells that express one or more polypeptides of GATA 4, Mef2c,myocardin, CD105⁺, CD90⁺, CD73⁺, CD44⁺, CD29⁺, and Stro-1. In variousembodiments, the cellular composition contains cells that fail toexpress detectable levels or express reduced levels (relative to areference cell) of a polypeptide that is any one or more of CD34⁺,CD45⁺, c-kit, and vascular pericyte marker.

In still another aspect, the invention provides an isolated epicardialprogenitor cell that expresses any one or more of epicardin, Nkx 2.5,Isl-1, GATA 5, WT1, Tbx18, and Tbx5. In various embodiments, theisolated epicardial progenitor cell expresses a polypeptide that is anyone or more of GATA 4, Mef2c, myocardin, CD105⁺, CD90⁺, CD73⁺, CD44⁺,CD29⁺, and Stro-1. In particular embodiments, the isolated epicardialprogenitor cell fails to express detectable levels or expresses reducedlevels of a polypeptide that is any one or more of CD34⁺, CD45⁺, c-kit,and vascular pericyte marker.

In another aspect, the invention provides an isolated population ofepicardial progenitor cells, where the epicardial progenitor cellsexpress any one or more of epicardin, Nkx 2.5, Isl-1, GATA 5, WT1,Tbx18, and Tbx5. In various embodiments, the epicardial progenitor cellsexpress a polypeptide that is any one or more of GATA 4, Mef2c,myocardin, CD105⁺, CD90⁺, CD73⁺, CD44⁺, CD29⁺, and Stro-1. In particularembodiments, the epicardial progenitor cells fail to express detectablelevels or expresses reduced levels of a polypeptide that is any one ormore of CD34⁺, CD45⁺, c-kit, and vascular pericyte marker.

The invention further provides a pharmaceutical composition comprisingone or more secreted cellular factors isolated from an epicardialprogenitor cell of any previous claim or otherwise delineated herein. Inone embodiment, the composition supports cardiac cell survival, growth,or proliferation.

In yet another aspect, the invention provides a method of culturing anisolated epicardial progenitor cell or progeny thereof that expressesany one or more of epicardin, Nkx 2.5, Isl-1, GATA 5, WT1, Tbx18, andTbx5, involving culturing an isolated epicardial progenitor cell orprogeny thereof on polystyrene. In particular embodiments, the isolatedepicardial progenitor cell or progeny thereof fails to undergoepithelial to mesenchymal transformation.

In various embodiments of any of the above aspects or any other aspectof the invention delineated herein, the epicardial progenitor cell orprogeny cell thereof expresses or is selected for expression of one ormore of epicardin, Nkx 2.5, Isl-1, GATA 5, WT1, Tbx18, and/or Tbx5polypeptides or polynucleotides. For example, the epicardial progenitorcell expresses one, two, three, four, five, six or seven of epicardin,Nkx 2.5, Isl-1, GATA 5, WT1, Tbx18, and/or Tbx5 polypeptides orpolynucleotides. In various embodiments of any of the above aspects orany other aspect of the invention delineated herein, the epicardialprogenitor cell or progeny cell thereof expresses a polypeptide that isany one or more of GATA 4, Mef2c, myocardin, CD105⁺, CD90⁺, CD73⁺,CD44⁺, CD29⁺, and Stro-1. In various embodiments of any of the aboveaspects, the epicardial progenitor cell or progeny cell thereof isselected for expression of one or more of a cell surface marker (e.g.,CD105⁺, CD90⁺, CD73⁺, CD44⁺, CD29⁺, and Stro-1). In particularembodiments, the epicardial progenitor cell or progeny cell thereof isselected for expression of one or more of a cell surface marker prior toselection for expression of an internal marker (e.g., epicardin, Nkx2.5, Isl-1, GATA 5, WT1, Tbx18, Tbx5, GATA 4, Mef2c, and/or myocardin).In various embodiments of any of the above aspects, the epicardialprogenitor cell or progeny cell thereof fails to express detectablelevels or expresses reduced levels of one or more of CD34⁺, CD45⁺,c-kit, and vascular pericyte marker.

In various embodiments of the above aspects or any other aspect of theinvention delineated herein, the epicardial progenitor cell or progenycell thereof is a human cell in vitro. In various embodiments of any ofthe above aspects delineated herein, the epicardial progenitor cell orprogeny cell thereof is an epithelial cell. In various embodiments, theepithelial cell or progeny cell thereof is isolated prior to, during, orsubsequent to epithelial-mesenchymal transformation (EMT). In stillother embodiments, a selected cell is capable of differentiating intoany one or more of myocytes, cardiac fibroblasts, smooth muscle cells,or endothelial cells.

In various embodiments of any of the above aspects, the secretedcellular factor is isolated from an epicardial progenitor cell selectedfor expression of any one or more of epicardin, Nkx 2.5, Isl-1, GATA 5,WT1, Tbx18, and Tbx5. In various embodiments, the cellular factor has abiological activity that is any one of more of reducing cell death in acell population at risk thereof, increasing cell survival, reducinginflammation, increasing epicardial cell proliferation, increasingepithelial to mesenchymal transformation, and increasing cardiacfunction. In various embodiments of any of the above aspects delineatedherein, the factor has a molecular weight that is at least about 5 kD.In other embodiments, the factor is inactivated by heat denaturation. Inother embodiments, the cellular factor is isolated from a primarycultured or a cell passaged for at least one, two, three, four, five,six or more passages.

In various embodiments of any of the above aspects delineated herein,the method reduces apoptosis or increases cell proliferation (e.g., analteration of at least about 5%, 10%, 20%, 25%, 50%, 75%, or 100%). Invarious embodiments of any of the above aspects delineated herein, themethod increases cardiac cell number or reduces cardiac cell death.

In particular embodiments, the method increases cardiac cell number byat least about 5%, 10%, 25%, 50%, 75%, 80%, 90% or 100% compared to acorresponding untreated control cardiac tissue or heart.

In various embodiments of any of the above aspects delineated herein,the composition is administered to a subject directly to a site ofcardiac tissue damage or cardiac disease or is administeredsystemically. In various embodiments of any of the above aspectsdelineated herein, the composition is administered to a subject directlyto a site of cardiac tissue damage or cardiac disease or is administeredsystemically. In various embodiments of any of the above aspectsdelineated herein, the subject has a disease or disorder that is any oneor more of myocardial infarction, congestive heart failure, stroke, andischemia. In various embodiments of any of the above aspects delineatedherein, the method prevents or ameliorates ischemic damage. Inparticular embodiments, the method prevents or ameliorates ischemicdamage in a cardiac tissue post-myocardial infarction.

In various embodiments of any of the above aspects delineated herein, areduction in cardiac tissue damage is indicated by a reduction in thetotal percentage of left ventricle with infarction, a reduction in thepercent of myocardial infarction in the anterior wall of the leftventricle, an increase in cardiac function, or a reduction in vascularrhexis. In various embodiments of any of the above aspects delineatedherein, an increase in cardiac function is indicated by increasedcardiac output, reduced left ventricular end diameter during diastole(LVEDD), improves echocardiography scoring for wall motion, increasesthe difference in left ventricle anterior wall thickness betweendiastole and systole, or improves percent fractional shortening.

In still other embodiments, a pharmaceutical composition of theinvention comprises one or more cellular factors isolated from acultured epicardial progenitor cell, and one or more recombinantcellular factors (e.g., HGF, VEGF, SDF-1 alpha, and/or IGF-1). In otherembodiments, the method involves identifying one or more of saidsecreted cellular factors. Once identified, the cellular factors may berecombinantly expressed and added to the pharmaceutical composition toincrease the concentration of such factors present in the composition.

In particular embodiments, the cellular factor is one or more of HGF,VEGF, SDF-1 alpha, and IGF-1. In other embodiments, a composition of theinvention contains or consists of HGF, VEGF, SDF-1 alpha and IGF-1. Inparticular embodiments, the amount of HGF is between about 3-500 ng/ml(e.g., 3, 4, 5, 10, 20, 30, 40, 50, 75, 100, 125, 150, 200, 225, 250,300, 350, 400, 450, 500 ng/ml), VEGF is between about 0.5-500 ng/ml(e.g., 0.5, 0.6, 0.7, 0.8, 0.9, 1, 2, 3, 4, 5, 10, 20, 30, 40, 50, 75,100, 125, 150, 200, 225, 250, 300, 350, 400, 450, 500 ng/ml), SDF-1alpha is between about 0.15 ng-500 ng/ml (e.g., 0.15, 0.2, 0.3, 0.4,0.5, 0.6, 0.7, 0.8, 0.9, 1, 2, 3, 4, 5, 10, 20, 30, 40, 50, 75, 100,125, 150, 200, 225, 250, 300, 350, 400, 450, 500 ng/ml), and IGF-1 isbetween about 0.03 ng-500 ng/ml (e.g., 0.3, 0.4, 0.5, 0.6, 0.7, 0.8,0.9, 1, 2, 3, 4, 5, 10, 20, 30, 40, 50, 75, 100, 125, 150, 200, 225,250, 300, 350, 400, 450, 500 ng/ml). In other embodiments, thecomposition comprises at least HGF, VEGF, and SDF or at least HGF andVEGF.

Other features and advantages of the invention will be apparent from thedetailed description, and from the claims.

Definitions

By “epicardial progenitor cell” is meant a cell that gives rise to acell of the epicardium, or a cell that expresses or whose progenyexpress any one or more of epicardin, Nkx 2.5, Isl-1, GATA 5, WT1,Tbx18, and Tbx5. In other embodiments, an epicardial progenitor cellexpresses one or more of GATA 4, Mef2c, myocardin, CD105⁺, CD90⁺, CD73⁺,CD44⁺, CD29⁺, and Stro-1. Exemplary amino acid sequences for theaforementioned polypeptides are known in the art and/or are describedherein at FIG. 11.

By “increasing epicardial cell proliferation” is meant increasing celldivision of an epicardial progenitor cell or a cell derived from anepicardial progenitor cell in vivo or in vitro. Increasing epicardialcell proliferation may also include promoting, supporting, or inducingthe differentiation and/or migration of epicardial cells. Epicardialcell proliferation may be measured by determining the number of cellsexpressing one or more of epicardin, Nkx 2.5, Isl-1, GATA 5, WT1, Tbx18,Tbx5 or any marker described herein (e.g., by fluorescence-activatedcell sorting). For example, an increase in cell number may be at leastabout a 5%, 10%, 15%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, or even100% increase in the number of epicardial cells relative to the numberof cells present in a naturally-occurring, corresponding cardiac tissueor heart.

By “cardiac protective activity” is meant any biological activity thatmaintains or increases the survival or function of a cardiac cell orcardiac tissue in vitro or in vivo.

By “cardiac function” is meant the biological function of cardiac tissueor heart (e.g., contractile function). Methods for measuring thebiological function of the heart are standard in the art (e.g., Textbookof Medical Physiology, Tenth edition, (Guyton et al., W.B. Saunders Co.,2000) and are also described herein. By “increasing in cardiac function”is meant an increase in a biological function of the heart by at leastabout 5%, 10%, 15%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, or even 100%relative to the biological function present in a naturally-occurring,corresponding cardiac tissue or heart.

By “cell survival” is meant cell viablility.

By “reducing cell death” is meant reducing the propensity or probabilitythat a cell will die. Cell death can be apoptotic, necrotic, or by anyother means.

By “reducing inflammation” is meant reducing the severity or symptoms ofan inflammatory reaction in a tissue. An inflammatory reaction withintissue is generally characterized by leukocyte infiltration, edema,redness, pain, neovascularization (in advanced cases), and finallyimpairment of function. Inflammation can also be measured by analyzinglevels of cytokines, C reactive protein, or any other inflammatorymarker.

By “cellular factor” is meant any biological agent produced by a cell.While cellular factors isolated from culture media are typicallysecreted by cells in culture, the scope of the invention is intended toinclude any factor released from a cultured cell into growth media. Inone embodiment, a cellular factor of the invention is secreted by a cellor is released into culture media when a cell breaks open and releasesits contents into the growth media. Exemplary cellular factors includeHGF, VEGF, SDF-1 alpha, and IGF-1.

By “epithelial to mesenchymal transformation” or “EMT” is meant aprogram of development of biological cells characterized by loss of celladhesion, repression of E-cadherin expression, and increased cellmobility. Epithelial to mesenchymal transformation plays a role innumerous developmental processes including mesoderm formation and neuraltube formation. Epithelial to mesenchymal transformation may be measuredby loss of cell adhesion, repression of E-cadherin expression, and/orincreased cell mobility. For example, an increase in cell mobility maybe a 5%, 10%, 15%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, or even 100%increase in the mobility of cells of epithelial cells relative to themobility of epithelial cells present in a naturally-occurring,corresponding tissue or organ.

By “vascular rhexis” is meant loss of vascular integrity followingreperfusion after myocardial infarction. Vascular rhexis can lead toprogressive loss of myocyte function, necrosis, and infarct expansion indamaged cardiac tissue. Vascular rhexis may be assessed by methods todetermine vascular damage (e.g., extravasation; cell death).

By “secreted cellular factor” is meant any biologically active agentthat a cell secretes during in vitro culture.

By “epicardin polypeptide” is meant a protein or fragment thereof havingat least about 85% identity to NCBI Accession No. NP_(—)938206, or thatbinds an antibody generated against the epicardin antigen.

By “epicardin nucleic acid molecule” is meant a polynucleotide encodinga epicardin polypeptide.

By “Nkx 2.5 or NK2 transcription factor related, locus 5 polypeptide” ismeant a protein or fragment thereof having at least about 85% identityto NCBI Accession No. BAA35181 or that binds an antibody generatedagainst the Nkx 2.5 antigen.

By “NK2 transcription factor related, locus 5 nucleic acid molecule” ismeant a polynucleotide encoding a Nkx 2.5 polypeptide.

By “GATA 4 or GATA binding protein 4 polypeptide” is meant a protein orfragment thereof having at least about 85% identity to NCBI AccessionNo. BAA11334 or that binds an antibody generated against the GATA 4antigen.

By “GATA 4 nucleic acid molecule” is meant a polynucleotide encoding aGATA 4 polypeptide.

By “GATA 5 or GATA binding protein 5 polypeptide” is meant a protein orfragment thereof having at least about 85% identity to NCBI AccessionNo. NP_(—)536721 or that binds an antibody generated against the GATA 5antigen.

By “GATA 5 nucleic acid molecule” is meant a polynucleotide encoding aGATA 5 polypeptide.

By “Tbx18 or T-box 18 polypeptide” is meant a protein or fragmentthereof having at least about 85% identity to NCBI Accession No.CAB37937 or that binds an antibody generated against the Tbx18 antigen.

By “Tbx18 nucleic acid molecule” is meant a polynucleotide encoding aTbx18 polypeptide.

By “Tbx5 or T-box 5” is meant a polypeptide or fragment thereof havingat least about 85% identity to NCBI Accession No. NP_(—)000183 or thatbinds an antibody generated against the Tbx5 antigen.

By “Tbx5 nucleic acid molecule” is meant a polynucleotide encoding aTbx5 polypeptide.

By “Wt1 or Wilms tumor 1 polypeptide” is meant a protein or fragmentthereof having at least about 85% identity to NCBI Accession No.NP_(—)000369 or that binds an antibody generated against the Wt1antigen.

By “Wt1 nucleic acid molecule” is meant a polynucleotide encoding a Wt1polypeptide.

By “Isl-1 or islet-1 transcription factor polypeptide” is meant aprotein or fragment thereof having at least about 85% identity to NCBIAccession No. NP_(—)002193 or that binds an antibody generated againstthe Isl-1 antigen.

By “Isl-1 nucleic acid molecule” is meant a polynucleotide encoding aIsl-1 polypeptide.

By “Mef2c or myocyte enhancer factor 2c” is meant a polypeptide orfragment thereof having at least about 85% identity to NCBI AccessionNo. NP_(—)002388 (isoform 1) or NCBI Accession No. NP_(—)001124477(isoform 2) or that binds an antibody generated against the Mef2cantigen.

By “Mef2c nucleic acid molecule” is meant a polynucleotide encoding aMef2c polypeptide.

By “myocardin polypeptide” is meant a protein or fragment thereof havingat least about 85% identity to NCBI Accession No. NP_(—)705832 or thatbinds an antibody generated against the myocardin antigen.

By “myocardin nucleic acid molecule” is meant a polynucleotide encodinga myocardin polypeptide.

By “agent” is meant any small molecule chemical compound, antibody,nucleic acid molecule, or polypeptide, or fragments thereof.

By “ameliorate” is meant decrease, suppress, attenuate, diminish,arrest, or stabilize the development or progression of a disease.

By “alteration” is meant a change (increase or decrease) in theexpression levels or activity of a gene or polypeptide as detected bystandard art known methods such as those described herein. As usedherein, an alteration includes a 10% change in expression levels,preferably a 25% change, more preferably a 40% change, and mostpreferably a 50% or greater change in expression levels.”

By “analog” is meant a molecule that is not identical, but has analogousfunctional or structural features. For example, a polypeptide analogretains the biological activity of a corresponding naturally-occurringpolypeptide, while having certain biochemical modifications that enhancethe analog's function relative to a naturally occurring polypeptide.Such biochemical modifications could increase the analog's proteaseresistance, membrane permeability, or half-life, without altering, forexample, ligand binding. An analog may include an unnatural amino acid.

In this disclosure, “comprises,” “comprising,” “containing” and “having”and the like can have the meaning ascribed to them in U.S. Patent lawand can mean “includes,” “including,” and the like; “consistingessentially of” or “consists essentially” likewise has the meaningascribed in U.S. Patent law and the term is open-ended, allowing for thepresence of more than that which is recited so long as basic or novelcharacteristics of that which is recited is not changed by the presenceof more than that which is recited, but excludes prior art embodiments.

By “deficiency of a particular cell-type” is meant fewer of a specificset of cells than are normally present in a tissue or organ not having adeficiency. For example, a deficiency is a 5%, 10%, 15%, 20%, 30%, 40%,50%, 60%, 70%, 80%, 90%, or even 100% deficit in the number of cells ofa particular cell-type (e.g., cardiomyocytes, epicardial progenitorcells, embryonic stem cells, endothelial cells, endothelial precursorcells, fibroblasts, neurons, adipocytes) relative to the number of cellspresent in a naturally-occurring, corresponding tissue or organ. Methodsfor assaying cell-number are standard in the art, and are described in(Bonifacino et al., Current Protocols in Cell Biology, Loose-leaf, JohnWiley and Sons, Inc., San Francisco, Calif., 1999; Robinson et al.,Current Protocols in Cytometry Loose-leaf, John Wiley and Sons, Inc.,San Francisco, Calif., October 1997).

“Derived from” as used herein refers to the process of obtaining a cellfrom a subject, embryo, biological sample, or cell culture.

“Detect” refers to identifying the presence, absence or amount of theobject to be detected.

By “detectable label” is meant a composition that when linked to amolecule of interest renders the latter detectable, via spectroscopic,photochemical, biochemical, immunochemical, or chemical means. Forexample, useful labels include radioactive isotopes, magnetic beads,metallic beads, colloidal particles, fluorescent dyes, electron-densereagents, enzymes (for example, as commonly used in an ELISA), biotin,digoxigenin, or haptens.

By “disease” is meant any condition or disorder that damages orinterferes with the normal function of a cell, tissue, or organ.Examples of diseases include any disease or injury that results in areduction in cell number or biological function, including ischemicinjury, such as stroke, myocardial infarction, or any other ischemicevent that causes tissue damage.

By “effective amount” is meant the amount of a required to amelioratethe symptoms of a disease relative to an untreated patient. Theeffective amount of active compound(s) used to practice the presentinvention for therapeutic treatment of a ischemic injury variesdepending upon the manner of administration, the age, body weight, andgeneral health of the subject. Ultimately, the attending physician orveterinarian will decide the appropriate amount and dosage regimen. Suchamount is referred to as an “effective” amount.

By “fragment” is meant a portion of a polypeptide or nucleic acidmolecule. This portion contains, preferably, at least 10%, 20%, 30%,40%, 50%, 60%, 70%, 80%, or 90% of the entire length of the referencenucleic acid molecule or polypeptide. A fragment may contain 10, 20, 30,40, 50, 60, 70, 80, 90, or 100, 200, 300, 400, 500, 600, 700, 800, 900,or 1000 nucleotides or amino acids.

By “isolated polynucleotide” is meant a nucleic acid (e.g., a DNA) thatis free of the genes which, in the naturally-occurring genome of theorganism from which the nucleic acid molecule of the invention isderived, flank the gene. The term therefore includes, for example, arecombinant DNA that is incorporated into a vector; into an autonomouslyreplicating plasmid or virus; or into the genomic DNA of a prokaryote oreukaryote; or that exists as a separate molecule (for example, a cDNA ora genomic or cDNA fragment produced by PCR or restriction endonucleasedigestion) independent of other sequences. In addition, the termincludes an RNA molecule that is transcribed from a DNA molecule, aswell as a recombinant DNA that is part of a hybrid gene encodingadditional polypeptide sequence.

By an “isolated polypeptide” is meant a polypeptide of the inventionthat has been separated from components that naturally accompany it.Typically, the polypeptide is isolated when it is at least 60%, byweight, free from the proteins and naturally-occurring organic moleculeswith which it is naturally associated. Preferably, the preparation is atleast 75%, more preferably at least 90%, and most preferably at least99%, by weight, a polypeptide of the invention. An isolated polypeptideof the invention may be obtained, for example, by extraction from anatural source, by expression of a recombinant nucleic acid encodingsuch a polypeptide; or by chemically synthesizing the protein. Puritycan be measured by any appropriate method, for example, columnchromatography, polyacrylamide gel electrophoresis, or by HPLC analysis.When a cellular factor is “isolated” from a cultured epicardialprogenitor cell the cellular factor is typically separated from cellsand cellular debris. It need not be purified to homogeneity. In fact,the composition comprising an isolated cellular factor typicallycomprises any number of cellular factors whose presence contributes tothe biological activity (e.g., growth promoting, survival promoting, orproliferation promoting activity) of the composition. In one embodiment,a composition of the invention comprises or consists of conditionedmedia from which cells and cellular debris have been removed. Ifdesired, the composition is supplemented with one or more recombinantpolypeptides (HGF VEGF SDF-1 alpha and IGF-1).

By “marker” is meant any protein or polynucleotide having an alterationin expression level or activity that is associated with a disease ordisorder.

As used herein, “obtaining” as in “obtaining an agent” includessynthesizing, purchasing, or otherwise acquiring the agent.

As used herein, the terms “prevent,” “preventing,” “prevention,”“prophylactic treatment” and the like refer to reducing the probabilityof developing a disorder or condition in a subject, who does not have,but is at risk of or susceptible to developing a disorder or condition.

By “reference” is meant a standard or control condition.

A “reference sequence” is a defined sequence used as a basis forsequence comparison. A reference sequence may be a subset of or theentirety of a specified sequence; for example, a segment of afull-length cDNA or gene sequence, or the complete cDNA or genesequence. For polypeptides, the length of the reference polypeptidesequence will generally be at least about 16 amino acids, preferably atleast about 20 amino acids, more preferably at least about 25 aminoacids, and even more preferably about 35 amino acids, about 50 aminoacids, or about 100 amino acids. For nucleic acids, the length of thereference nucleic acid sequence will generally be at least about 50nucleotides, preferably at least about 60 nucleotides, more preferablyat least about 75 nucleotides, and even more preferably about 100nucleotides or about 300 nucleotides or any integer thereabout or therebetween.

By “substantially identical” is meant a polypeptide or nucleic acidmolecule exhibiting at least 50% identity to a reference amino acidsequence (for example, any one of the amino acid sequences describedherein) or nucleic acid sequence (for example, any one of the nucleicacid sequences described herein). Preferably, such a sequence is atleast 60%, more preferably 80% or 85%, and more preferably 90%, 95% oreven 99% identical at the amino acid level or nucleic acid to thesequence used for comparison.

Sequence identity is typically measured using sequence analysis software(for example, Sequence Analysis Software Package of the GeneticsComputer Group, University of Wisconsin Biotechnology Center, 1710University Avenue, Madison, Wis. 53705, BLAST, BESTFIT, GAP, orPILEUP/PRETTYBOX programs). Such software matches identical or similarsequences by assigning degrees of homology to various substitutions,deletions, and/or other modifications. Conservative substitutionstypically include substitutions within the following groups: glycine,alanine; valine, isoleucine, leucine; aspartic acid, glutamic acid,asparagine, glutamine; serine, threonine; lysine, arginine; andphenylalanine, tyrosine. In an exemplary approach to determining thedegree of identity, a BLAST program may be used, with a probabilityscore between e⁻³ and e⁻¹⁰⁰ indicating a closely related sequence.

By “repair” is meant to ameliorate damage or disease in a tissue ororgan.

By “tissue” is meant a collection of cells having a similar morphologyand function.

As used herein, the terms “treat,” treating,” “treatment,” and the likerefer to reducing or ameliorating a disorder and/or symptoms associatedtherewith. It will be appreciated that, although not precluded, treatinga disorder or condition does not require that the disorder, condition orsymptoms associated therewith be completely eliminated.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A-1P depict the isolation of epicardial stem/progenitor cells.FIGS. 1A-1H are micrographs of epicardial stem/progenitor cells invitro. FIG. 1A depicts an explant culture of right atrial appendage togenerate feeder layer. FIG. 1B depicts the formation of floatingspheroids and bunches of cells following switch to medium that favorsthe growth of stem/progenitor cells. FIG. 1C depicts maintenance ofepicardial stem/progenitor cells with epithelial phenotype on uncoateddishes. FIG. 1D depicts epithelial to mesenchymal transformation (EMT)at 3 days following collection and transfer of floating cells (arrows:some cells do not undergo EMT and remain epithelial-like). FIG. 1Edepicts epicardial cells with the epithelial phenotype expressingkeratin proteins, while derived precursors express vimentin but notkeratin. FIG. 1F-1H depict immunocytochemistry for transcription factorsassociated with cardiac development and repair: Epicardin, Nkx 2.5, GATA4, respectively. FIGS. 1I and 1J depict non-specific Rabbit IgG andnon-specific Mouse IgG staining controls, respectively, forimmunocytochemistry experiments. FIG. 1K shows an analysis of mRNAexpression using reverse transcriptase polymerase chain reaction(RT-PCR). Several transcription factors associated with cardiacdevelopment are downregulated during differentiation while others suchas smooth muscle actin (SMA) and von Willebrand Factor (vWF) areupregulated. Left lane shows amplification from RNA of cells from stemcells (e.g., as shown in FIG. 1C). Center and right lanes showamplification of RNA from cells after 1 and 2 weeks of culture on coatedcellware. Note: the lower diffuse bands in the gel data for GATA5,Isl-1, and Tbx5 are primer dimers. FIG. 1L shows an analysis of mRNAexpression in epicardially-derived precursor cells derived from 3 humandonors (passage 0) using reverse transcriptase polymerase chain reaction(RT-PCR) for cardiac transcription factors (GATA 4, MEF2c, andmyocardin). FIG. 1M depicts epicardial cell outgrowth from epicardialexplant generated by dissecting surface epicardial cell layer from rightatrial appendage removed during bypass surgery. Outgrowth occurred over7 d. Note epithelial morphology of cell monolayer. FIG. 1N depictsepicardial cell monolayer 1d after switching medium to adultstem/progenitor expansion medium (see Methods). FIG. 1O depictsepicardial cell monolayer 3 d after switching medium to adultstem/progenitor expansion medium. Note refractile cells beginning toround up. FIG. 1P depicts epicardial cell monolayer 4 d after switchingmedium to adult stem/progenitor expansion medium. Note the formation of“bunches of grapes” due to epicardial progenitor-like cells adhering toeach other and growing upward in the culture dish (within yellowdashes). In the isolation methods described herein, the bunches ofprogenitor cells pictured in FIG. 1P could be gathered and transferredto a medium containing 10% FCS to induce EMT.

FIGS. 2A-2M depict the expansion of atrial progenitor cells afterepithelial to mesenchymal transformation (EMT). FIGS. 2A-2L arefluorescence micrographs of cells in culture. FIGS. 2A-2D depictexpression of contractile proteins associated with cardiac myocytes:cardiac alpha actin (10×), cardiac alpha actin (40×), and phosphorylatedmyosin light chain (MCLPS20 and MLC2v). Note that cardiac alpha actin isnot organized into mature sarcomeres. FIGS. 2E and 2F depictimmunocytochemistry for markers of smooth muscle cells and endothelialcells: smooth muscle myosin (SMM) and von Willebrand Factor (vWF),respectively. Arrows indicate positive cells. FIGS. 2G and 2H depict theexpression of gap junction proteins Cx40 and Cx43, respectively (arrows:Cx43 localization at membrane interaction between cells). FIGS. 2I and2J depict the expression of the calcium binding protein Calsequestrinand the calcium ATPase SERCA2a, respectively. FIG. 2K shows that asubset of atrial progenitors express the MSC marker Stro-1 (arrow:positive cell; arrowhead: negative cell). FIG. 2L depicts non-specificmouse IgM staining control for immunocytochemistry experiments. FIG. 2Mdepicts results of a reverse transcriptase polymerase chain reaction(RT-PCR) for cardiac lineage mRNAs (cardiac alpha actin, MLC4, MLC2a,MLC2v, alpha SMA, vWF, Connexin 43, SERCA2a) derived from 3 humandonors.

FIGS. 3A and 3B show results of FACS analysis for cell surface epitopes(Stro-1, CD 146, CD105, CD90, CD73, CD54, CD49d, CD44, CD31, CD29, CD24,c-kit, NG2, CD45, and CD34) in epicardial progenitors after epithelialto mesenchymal transformation (EMT) of two isolation procedures. Notethat the expanding cell population was negative for CD45 and CD34 aswell as c-kit. Many of the cells were positive for markers associatedwith MSCs: CD105, CD90, CD73, CD44, CD29 and Stro-1. In FIG. 3A, thegreen line represents the signal from cells (isolated using method#1)stained with isotype control antisera and the red line represents thesignal from cells from the same culture stained with the specificantisera. In FIG. 3B, the red line represents the signal from cells(isolated using method#2) stained with isotype control antisera and thegreen line represents the signal from cells from the same culturestained with the specific antisera.

FIGS. 4A-4C are graphs showing the results of intra-arterialadministration of concentrated conditioned medium (CdM) from humanatrial progenitor cells on cardiac function in immunodeficient mice 1week after myocardial infarction (MI) with reperfusion. CdM from humanatrial progenitor cells improves cardiac function in immunodeficientmice after myocardial infarction with reperfusion. FIG. 4A shows thattreatment with CdM significantly increases (improves) percent fractionalshortening after MI compared to treatment with vehicle alone (alphaMinimum Essential Medium; alpha MEM) (*** p≦0.001). FIG. 4B shows thattreatment with CdM significantly increases the difference in leftventricle anterior wall thickness between diastole and systole comparedto treatment with vehicle alone (alpha Minimum Essential Medium; alphaMEM) (*** p≦0.001). FIG. 4C shows that treatment with CdM significantlydecreases (improves) echocardiography scoring for wall motion comparedto treatment with vehicle alone (alpha Minimum Essential Medium; alphaMEM) (** p≦0.01). (scale: ECHO score 13=Full wall motion; ECHO score39=total akinesis). Sham operated mice underwent all procedures exceptthat the suture was passed under the LAD and not tied; CdM or alpha MEM(vehicle control) was administered intra-arterially at the time ofreperfusion after 4 hours of ischemia (Sham, n=2; CdM, n=8; alpha MEM,n=6).

FIGS. 5A and 5B are graphs showing myocardial infarct (MI) size forimmunodeficient mice as determined by creatine kinase (CK) activity.FIG. 5A shows that treatment with CdM significantly decreases (improves)percent of myocardial infarction in the anterior wall of the leftventricle (LV) compared to treatment with vehicle alone (alpha MinimumEssential Medium; alpha MEM) (*** p≦0.001). FIG. 5B shows that treatmentwith CdM significantly decreases (improves) total percentage of leftventricle with infarction compared to treatment with vehicle alone(alpha Minimum Essential Medium; alpha MEM) (** p≦0.01). Sham operatedmice underwent all procedures except that the suture was passed underthe LAD and not tied; CdM or alpha MEM (vehicle control) wasadministered intra-arterially at the time of reperfusion after 4 hoursof ischemia (Sham, n=2; CdM, n=8; Alpha MEM, n=7).

FIGS. 6A-6C are representative M Mode images and electrocardiograms(ECG) of Sham (FIG. 6A), CdM-treated (FIG. 6B), or Alpha MEM-treated(FIG. 6C) immunocompetent mice 1 week after myocardial infarction (MI).

FIGS. 7A-7C are graphs showing the results of intra-arterialadministration of concentrated conditioned medium (CdM) from humanatrial progenitor cells on cardiac function in immunodeficient mice 1week after myocardial infarction (MI) with reperfusion. CdM from humanatrial progenitor cells improves cardiac function in immunocompetentmice after myocardial infarction with reperfusion. FIG. 7A shows thattreatment with CdM significantly increases (improves) percent fractionalshortening after MI compared to treatment with vehicle alone (alphaMinimum Essential Medium; alpha MEM) (** p≦0.01). FIG. 7B shows thattreatment with CdM significantly increases the difference in leftventricle anterior wall thickness between diastole and systole comparedto treatment with vehicle alone (alpha Minimum Essential Medium; alphaMEM) (** p≦0.01). FIG. 7C shows that treatment with CdM significantlydecreases (improves) echocardiography scoring for wall motion comparedto treatment with vehicle alone (alpha Minimum Essential Medium; alphaMEM) (*** p≦0.001) (scale: ECHO score 13=Full wall motion; ECHO score39=total akinesis). Sham operated mice underwent all procedures exceptthat the suture was passed under the LAD and not tied; CdM or alpha MEM(vehicle control) was administered intra-arterially at the time ofreperfusion after 4 hours of ischemia (Sham, n=2; CdM, n=7; Alpha MEM,n=7).

FIGS. 8A and 8B are graphs showing end left ventricular diameter duringsystole (LVESD) and end left ventricular diameter during diastole(LVEDD) in immunocompetent mice. Improvement in left ventriculardimensions during systole and diastole in CdM-treated immunocompetentmice. FIG. 8A shows that treatment with CdM significantly decreases endleft ventricular diameter during systole (LVESD) compared to treatmentwith vehicle alone (alpha Minimum Essential Medium; alpha MEM) (**p≦0.01). FIG. 8B shows that treatment with CdM significantly decreasesend left ventricular diameter during diastole (LVEDD) compared totreatment with vehicle alone (alpha Minimum Essential Medium; alpha MEM)(* p≦0.05). Sham operated mice underwent all procedures except that thesuture was passed under the LAD and not tied; CdM or alpha MEM (vehiclecontrol) was administered intra-arterially at the time of reperfusionafter 4 hours of ischemia (Sham, n=2; CdM, n=7; Alpha MEM, n=7).

FIG. 9 is a graph showing cardiac output in immunocompetent mice. CdMtreatment significantly improves cardiac output after MI inimmunocompetent mice compared to treatment with vehicle alone (alphaMinimum Essential Medium; alpha MEM) (**** p≦0.0001). Cardiac output wascalculated from pulmonary arterial Doppler. Sham operated mice underwentall procedures except that the suture was passed under the LAD and nottied; CdM or alpha MEM (vehicle control) was administeredintra-arterially at the time of reperfusion after 4 hours of ischemia(Sham, n=2; CdM, n=7; Alpha MEM, n=7).

FIGS. 10A-10G show that EPI CdM treatment reduced infarct size at 1 wkafter MI and reperfusion and improved cardiac function ofimmunocomeptent (C57bl6/J) mice at 1 month after MI and reperfusion.FIG. 3A depicts Gomori trichrome stains of representative histologicalsections from Alpha MEM-treated (left) and EPI CdM-treated (right)immunocompetent mice with MI. Arrowheads delineate extent of infarct.Scale bar=100 μM. FIG. 10B shows that treatment with CdM significantlydecreases (improves) percent of myocardial infarction in the anteriorwall of the left ventricle compared to treatment with vehicle alone(alpha Minimum Essential Medium; alpha MEM) (*** p≦0.001). FIG. 10Cshows that treatment with CdM significantly decreases (improves) totalpercentage of left ventricle with infarction compared to treatment withvehicle alone (alpha Minimum Essential Medium; alpha MEM) (** p≦0.01).Sham operated mice underwent all procedures except that the suture waspassed under the LAD and not tied; CdM or alpha MEM (vehicle control)was administered intra-arterially at the time of reperfusion after 4hours of ischemia. (Sham, n=2; CdM, n=5; Alpha MEM, n=7). FIG. 10D is agraph depicting percent fractional shortening in EPI CdM-treatedcompared with Alpha MEM (vehicle)-treated mice. FIG. 10E is a graphdepicting echocardiography scoring for wall motion. Note: Full wallmotion would score a 13; total akinesis would score a 39. FIG. 10F is agraph depicting end left ventricular diameter in systole (LVESD). FIG.10G is a graph dpeicting cardiac output calculated from pulmonaryarterial flow (Doppler measurement). EPI CdM or Alpha MEM (vehicle, MEM)was administered intra-arterially at the time of reperfusion after 4hours of ischemia. Sham, n=2; EPI CdM, n=3; Alpha MEM, n=5. Note thatfor (d), Alpha MEM, n=4. * P≦0.05, ** P≦0.01, *** P≦0.001; compared withAlpha MEM. Error bars, SD.

FIG. 11 provides exemplary sequences of human epicardin (SEQ ID NO: 35),Nkx 2.5 (SEQ ID NO: 36), Isl-1(SEQ ID NO: 42), GATA 5 (SEQ ID NO: 38),WT1 (SEQ ID NO: 41), Tbx18 (SEQ ID NO: 39), Tbx5 (SEQ ID NO: 40), GATA 4(SEQ ID NO37), Mef2c (isoform 1 disclosed as SEQ ID NO: 43, isoform 2disclosed as SEQ ID NO: 44), and myocardin (SEQ ID NO: 45) polypeptides.

FIGS. 12A-12G show that EPI CdM treatment significantly reduced cardiacnecrosis at 24 hours after myocardial infarction with reperfusion. FIGS.12A 12F are micrographs. FIG. 12A shows immunohistochemical detection ofsingle-stranded DNA (ssDNA) to detect apoptotic cells in positivecontrol thymus tissue. Widespread apoptosis is present in the thymus ofthe dexamethasone (Dex)-treated mouse. FIG. 12B shows that apoptosis isminimal in hearts within the region of infarction at 24 hrs after MIwith reperfusion. Arrow: Single apoptotic cell (ssDNA-positive). FIGS.12C and 12D show representative TUNEL staining indicating widespreadnecrosis within regions of infarction for control Alpha MEM-treated miceat 24 hours after reperfusion. TUNEL-positive cells are green (FITC).FIGS. 12E and 12F show representative TUNEL staining demonstrating asignificant reduction in the numbers of necrotic cells in mouse heartstreated with EPI CdM at the time of reperfusion compared with controls.FIG. 12G is a graph showing a quantification of TUNEL positive cells at24 hours after MI with reperfusion. Alpha MEM, N=4; EPI CdM, N=3. Serialsections were cut to span the region of infarction. Six differentsections spanning the region of infarction were quantified for eachmouse heart.

FIGS. 13A-13L are graphs showing that HGF is a cardioprotective andvasoprotective component of EPI CdM. FIG. 13A quantitates ELISA datashowing the amount of HGF in unconcentrated 1×EPI CdMs of 5 human donorsthat range in age (52-80 yrs). FIG. 13B shows that regardless of donorage, 1×EPI CdM protects primary human aortic endothelial cells duringsimulated ischemia (1% oxygen for 24 hrs). GM: endothelial cell growthmedium. Alpha MEM: low glucose base medium (CdM vehicle). FIGS. 13C-Fshow that antibody neutralization of HGF in 10×EPI CdM significantlyreduced long-term (48 hr) protection of simulated ischemia for bothprimary aortic endothelial cells (FIGS. 13C and 13D) and primary humancoronary artery endothelial cells (FIGS. 13E and 13F). IgG controls andHGF were both added to EPI CdM at 10 micrograms/ml. MTS assay measurescell metabolism. Cell numbers were determined by CyQuant assay (dyebinding of nuclei acids). FIGS. 13G-13L are graphs showing that HGFpulldown from EPI CdM significantly reduced the benefits EPI CdMconferred on cardiac function at 1 wk after MI and reperfusion asdetermined by percent fractional shortening (FS, FIG. 13G), ECHO wallmotion score (E score, h), and left ventricular end diameter in systole(LVESD, FIG. 13I). FIG. 13J is a graph showing that cardiac outputmeasured from the pulmonary artery did not differ between mice with MItreated with HGF-PD compared with those that received IgG-PD. FIGS. 13Kand 13L are graphs showing HGF pulldown from EPI CdM significantlyreduced the amount of myocardial tissue preserved at 1 wk after MI andreperfusion. FIG. 13K is a graph depicting CK assay of anterior leftventricle wall (CK AW). FIG. 13K is a graph depicting CK assay of totalleft ventricle (CK total LV). Animal numbers (g-j): Sham, n=2; AlphaMEM, n=7; EPI CdM IgG-PD, n=8-9; EPI CdM HGF-PD, n=10. Animal numbers(k,1): Sham, n=2; Alpha MEM, n=8; EPI CdM IgG-PD, n=9; EPI CdM HGF-PD,n=10. * P≦0.05, ** P≦0.01, *** P≦0.001, NS=no significant difference.Error bars, SD.

FIG. 14 provides graphs showing a quantification of secreted proteinspresent in 1×EPI CdM. Data are shown for 5 different human donors. AllELISA data are in triplicate.

FIG. 15 is a graph showing that a pulldown (PD) method depleted growthfactors from 30×EPI CdM. HGF PD using biotinylated primary antiseraspecific to HGF removes all detectable HGF from EPI CdM. HGF ELISA showsthat incubation of EPI CdM in biotinylated non-specific IgG from thesame host species does not affect HGF concentration compared withoriginal EPI CdM. Samples were incubated in strepavidin conjugatedagarose to remove antibody complexes during centrifugation. ELISA dataare shown in triplicate.

FIGS. 16A-16C show Intra-coronary EPI CdM infusion at reperfusionpreserves cardiac tissue in adult swine after MI. FIG. 16A showsrepresentative 1 cm slices from control and EPI CdM-treated heartsstained by TTC at 24 hrs after 1 hr of ischemia with reperfusion. Notethat the non-viable (white) area in the control heart extends throughthe 3^(rd) (bottom) section in both the LV and RV, while the infarct inthe EPI CdM-treated heart does not. FIG. 16B shows that EPI CdMtreatment significantly reduced infarct size at 24 hrs after MI(P=0.024, control vs.EPI CdM-treated, n=5 each). FIG. 16C shows islandsof viable myocardium rescued in the apex of a heart treated with 25×EPICdM (arrows). Error bars, SD of mean.

FIGS. 17A-17G show that multiple vasoprotective factors in EPI CdM actedin concert to prevent vascular rhexis after MI and reperfusion FIGS.17A-17D are images depicting vascular integrity at 24 hrs after MI andreperfusion using extravasation of FITC-conjugated albumin (FITC-Alb) asan indicator. Note that areas of TUNEL staining for cardiac necrosis(FIG. 17B) correlate with areas containing FITC-Alb (see merge, FIG.17D). Yellow arrows indicate TUNEL-positive cells (FIGS. 17B-17D). FIGS.17E-17F show that at 24 hrs after reperfusion, hearts from AlphaMEM-treated control mice contained extensive extravasated FITC-Alb thatwas significantly decreased by EPI CdM treatment (EPI CdM IgG-PD). Incontrast, simultaneous pulldown of HGF, VEGFA, and SDF-1 alpha (EPI CdM3 GF PD) abrogated the ability of EPI CdM treatment to prevent vascularrhexis and associated cardiac tissue necrosis. Note that hearts fromSham-operated mice (pictured in FIG. 17E) did not contain areas ofextravastated FITC-Alb and are therefore not represented in (FIG. 17F).Scale bars in FIG. 17E=50 μM. FIG. 17G is a graph depicting ELISA ofserum PTX3 levels at 24 hrs after reperfusion as an independent measureof vascular rhexis. EPI CdM treatment (EPI CdM IgG-PD) significantlyreduced the level of circulating PTX3, demonstrating prevention ofvascular rhexis after reperfusion. In agreement with the determinationof LV mural volumes containing FITC-Alb (FIG. 17F), mice treated withEPI CdM 3 GF PD have serum levels of PTX3 that did not differ from thoseof Alpha MEM-treated control mice. Animal numbers (FIG. 17F): Alpha MEM,n=4; EPI CdM IgG-PD, n=6; EPI CdM 3 GF PD, n=4. Animal numbers (FIG.17G): Sham, n=3; Alpha MEM, n=5; EPI CdM IgG-PD, n=6; EPI CdM 3 GF PD,n=5. * P≦0.05, ** P≦0.01, †=no significant difference. Error bars, SD.

FIGS. 18A-18C depict images of a FITC-Alb extravasation assay forvascular integrity after MI and reperfusion. FIGS. 18A and 18B provideepifluorescent micrographs and Differential Interference Contrast (DIC)images that illustrate the high resolution of FITC-Alb assay. Merge inFIG. 18B demonstrates tagging of individual cardiac myocytes adjacent toFITC-negative myocytes. FIG. 18C shows extensive tissue necrosis withinareas of myocardium that were positive for extravasated FITC-Alb asdetermined by TUNEL assays. Note that pink nuclei are positive for TUNELstaining. Nuclei are shown by DAPI staining.

DETAILED DESCRIPTION OF THE INVENTION

The invention features therapeutic compositions comprising agentssecreted by epicardial progenitor cells and/or epicardialprogenitor-derived mesenchymal stem cells and methods of using suchcompositions for the repair or regeneration of damaged cardiac tissue orheart.

The present invention is based, at least in part, on the discoveriesthat media isolated from epicardial progenitor cells or epicardialprogenitor-derived mesenchymal stem (EPI CdM) preserved cardiacfunction, reduced cell death, reduced inflammatory responses, andpromoted healing of injured tissues and prevention of vascular rhexis inthe mice when administered intra-arterially to mice after prolongedmyocardial ischemia (4 hours) with reperfusion. Without intending to bebound to theory, EPI CdM treatment rapidly reduces myocardial necrosisand infarct expansion after MI by preventing the progression of vascularrhexis that occurs following reperfusion. Treatment using EPI CdMprovides advantages over cell-based therapies, which involve invasiveisolation procedures, lack of available autologous materials, or therequirement for MHC-matching. Unexpectedly and surprisingly, EPI CdMfrom patients of advanced age did not reduce the ability of EPI CdM toprovide cardioprotection or vasoprotection.

Accordingly, the invention provides therapeutic and prophylacticcompositions comprising agents secreted by epicardial progenitor cellsand/or epicardial progenitor-derived mesenchymal stem cells (e.g., HGFVEGF SDF-1 alpha and IGF-1) and methods of using such compositions toreduce cardiac cell death, preserve cardiac function after an ischemicevent, and to generally prevent cardiac damage and promote cardiachealing or regeneration.

Epicardial Progenitor Cells

The epicardium is a specialized epithelial cell layer that covers theheart and is important in maintaining cardiac structure and function(Gittenberger-de Groot et al., Circ Res. 2000; 87:969-971; Eralp et al.,Circ Res. 2005; 96:526-534). During cardiac development, a subset ofepicardial cells undergo epithelial to mesenchymal transformation,invade the underlying subepicardium and myocardium, and contribute tothe interstitial fibroblasts and the subepicardial and coronaryvasculature (Dettman et al., Dev Biol. 1998; 193:169-181; VranckenPeeters et al., Anat Embryol (Berl). 1999; 199:367-378; Pérez-Pomares etal., Int J Dev Biol. 2002; 46:1005-1013; Reese et al., Circ Res. 2002;91:761-768). Recent genetic lineage tracing studies have demonstratedthat epicardial progenitor cells also contribute extensively to thecardiac myocyte pool (Cai et al., Nature. 2008; 454:104-108). Thedramatic cardiac regeneration that occurs in adult zebrafish afterventricular injury depends upon on epicardial cell proliferation,epithelial-to-mesenchymal transition, invasion and subsequentneovascularization of myocardium (Lepilina et al., Cell. 2006;127:607-619). Because of their ability to respond to injury and todifferentiate into multiple cardiac cell types (Limana et al., Circ Res.2007; 101:1255-1265), epicardial cells and their derivatives can beconsidered as a potential source of post-natal cardiac stem/progenitorcells for regenerative medicine (Wessels et al., Anat Rec A Discov MolCell Evol Biol. 2004 January; 276(1):43-57; Winter et al., Circulation.2007; 116:917-927).

Isolation of Cells

While the results reported herein provide specific examples of theisolation of epicardial progenitor cells from right atrial appendages,the invention is not so limited. The unpurified source of cells for usein the methods of the invention may be any cells or tissue capable ofgiving rise to epicardial progenitor cells, embryonic stem cells, andinduced pluripotent cells (Wernig et al. Nature 19; 448(7151):318-24,2007). Preferably, cells of the invention are epicardial progenitorcells selected for expression of epicardin, Nkx 2.5, Isl-1, GATA 5, WT1,Tbx18, and Tbx5 transcription factors. In various embodiments, theepicardial progenitor cells are selected for expression of one or moreof a cell surface marker (e.g., CD105⁺, CD90⁺, CD73⁺, CD44⁺, CD29⁺, andStro-1) prior to selection for expression of an internal marker (e.g.,epicardin, Nkx 2.5, Isl-1, GATA 5, WT1, Tbx18, Tbx5, GATA 4, Mef2c,and/or myocardin. Various techniques can be employed to separate orenrich for the desired cells. Such methods include a positive selectionfor cells expressing these markers. Monoclonal antibodies areparticularly useful for identifying markers associated with the desiredcells. If desired, negative selection methods can be used in conjunctionwith the methods of the invention to reduce the number of irrelevantcells present in a population of cells selected for epicardin, Nkx 2.5,Isl-1, GATA 5, WT1, Tbx18, and Tbx5 expression. For example, epicardialprogenitor cells may be negatively selected for hematopoietic cellsurface markers such as CD34, CD45, c-kit, and the vascular pericytemarker NG2.

In one approach, epicardial progenitor cells are isolated by theselective culture of cells obtained from cardiac tissue (e.g., rightatrial appendage) in medium favoring stem/progenitor cell growth (e.g.,DMEM/F12 (Invitrogen) with 3% FCS (Atlanta Biologicals) and 20 ng/mlepidermal growth factor (EGF), 10 ng/ml basic fibroblast growth factor(bFGF), 10 ng/ml leukocyte migration inhibitory factor (LIF) (all growthfactors from Sigma, Saint Louis, Mo.), 1×1× insulin, transferrin,selenium (ITS plus) (BD Biosciences, San Jose, Calif.), 100 units/mlpenicillin, 100 μg/ml streptomycin, and 2 mM L-glutamine (MediatechInc.). In mixed cell cultures, epicardial progenitor cells aredistinguishable by their morphology and pattern of growth (e.g.,epicardial progenitor cells do not readily mix with other cells inculture; epicardial progenitor cells form spheroids or clusters ofspheriods that proliferate upwards into the medium rather thanhorizontally). Epicardial progenitor cells can be collected from mixedcultures by shaking the culture to release the loosely adherentaggregates and spheroids of stem/progenitor cells.

Other procedures that may be used for selection of cells of interestinclude, but are not limited to, density gradient centrifugation, flowcytometry, magnetic separation with antibody-coated magnetic beads,affinity chromatography, cytotoxic agents joined to or used inconjunction with a mAb, including, but not limited to, complement andcytotoxins; and panning with antibody attached to a solid matrix or anyother convenient technique. The cells can be selected against deadcells, by employing dyes associated with dead cells such as propidiumiodide (PI). Preferably, the cells are collected in a medium comprising(alpha MEM), fetal calf serum (FCS), or bovine serum albumin (BSA) orany other suitable, preferably sterile, isotonic medium. Selected cellsof the invention may be employed for the isolation of secreted cellularfactors as described herein.

In one embodiment, selected cells of the invention comprise a purifiedpopulation of epicardial progenitor cells selected for expression ofepicardin, Nkx 2.5, Isl-1, GATA 5, WT1, Tbx18, and Tbx5. Those skilledin the art can readily determine the percentage of cells in a populationusing various well-known methods, such as fluorescence activated cellsorting (FACS). Preferable ranges of purity in populations comprisingselected cells are about 50 to about 55%, about 55 to about 60%, andabout 65 to about 70%. More preferably the purity is at least about 70%,75%, or 80% pure, more preferably at least about 85%, 90%, or 95% pure.In some embodiments, the population is at least about 95% to about 100%selected cells.

The selected cells may be grown in culture for hours, days, or evenweeks during which time their culture medium becomes enriched in one ormore secreted cellular factors that support cardiac progenitor cellproliferation, reduce cardiac cell death, preserve cardiac functionafter an ischemic event, prevent or reduce cardiac damage, increasecardiac function, increase cardiac healing or increase cardiacregeneration. Media enriched for such biologically active agents istermed “conditioned media.”

Media and reagents for tissue culture are well known in the art (see,for example, Pollard, J. W. and Walker, J. M. (1997) Basic Cell CultureProtocols, Second Edition, Humana Press, Totowa, N.J.; Freshney, R. I.(2000) Culture of Animal Cells, Fourth Edition, Wiley-Liss, Hoboken,N.J.). Examples of suitable media for incubating mesenchymal stem cellsor multipotent stromal cells samples include, but are not limited to,Dulbecco's Modified Eagle Medium (DMEM), RPMI media, Hanks' BalancedSalt Solution (HBSS) phosphate buffered saline (PBS) and other mediaknown in the art. Examples of appropriate media for culturing cells ofthe invention include, but are not limited to, Dulbecco's Modified EagleMedium (DMEM), RPMI media. The media may be supplemented with fetal calfserum (FCS) or fetal bovine serum (FBS) as well as antibiotics, growthfactors, amino acids, inhibitors or the like, which is well within thegeneral knowledge of the skilled artisan.

If desired, the epicardial progenitor cells or their progeny is culturedunder conditions that maintain the cells in a proliferative state. Inone embodiment, the cells are immortalized to enhance theirproliferation. Methods for immortalizing a cell are known in the art andinclude, but are not limited to, expressing in the cell one or more ofdominant negative p53, telomerase, beta catenin, notch and/or atranscription factor or other polypeptide that promotes cellproliferation (e.g., stem cell proliferation). The aforementionedpolypeptides may be expressed using any vector suitable for expressionin an epicardial progenitor cell (e.g., a viral vector).

Formulations

In one embodiment, a composition of the invention comprises or consistsessentially of one or more cellular factors isolated from selectedepicardial progenitor cells or their progeny. In particular embodiments,the cellular factor is secreted by an epicardial progenitor cellselected for expression of epicardin, Nkx 2.5, GATA 4, Mef2c, andmyocardin polypeptides, polynucleotides, or the cellular progeny of aselected cell. Such cells are cultured according to any method known inthe art. In another embodiment, a composition of the invention comprisesconditioned media obtained during the culture of such cells thatcontains one or more biologically active agents secreted by a cell ofthe invention. If desired, the secreted cellular factors are at leastpartially purified (e.g., at least about 10%, 25%, 30%, 50%, 75%, 80%,90%, or 95%) to remove undesired agents present in the culture media. Inone embodiment, one or more identified cellular factors (e.g., HGF,VEGF, SDF-1 alpha, and/or IGF-1) is expressed recombinantly and used tosupplement a composition of the invention. The biologically activeagents present in the condition media, the cells, or a combinationthereof, can be conveniently provided to a subject as sterile liquidpreparations, e.g., isotonic aqueous solutions, suspensions, emulsions,dispersions, or viscous compositions, which may be buffered to aselected pH. Cells and agents of the invention may be provided as liquidor viscous formulations. For some applications, liquid formations aredesirable because they are convenient to administer, especially byinjection. Where prolonged contact with a tissue is desired, a viscouscomposition may be preferred. Such compositions are formulated withinthe appropriate viscosity range. Liquid or viscous compositions cancomprise carriers, which can be a solvent or dispersing mediumcontaining, for example, water, saline, phosphate buffered saline,polyol (for example, glycerol, propylene glycol, liquid polyethyleneglycol, and the like) and suitable mixtures thereof.

Sterile injectable solutions are prepared by compositions comprising asecreted cellular factor isolated from cultures of epicardial progenitorcells in the required amount of the appropriate solvent with variousamounts of the other ingredients, as desired. Such compositions may bein admixture with a suitable carrier, diluent, or excipient, such assterile water, physiological saline, glucose, dextrose, or the like. Thecompositions can also be lyophilized. The compositions can containauxiliary substances such as wetting, dispersing, or emulsifying agents(e.g., methylcellulose), pH buffering agents, gelling or viscosityenhancing additives, preservatives, flavoring agents, colors, and thelike, depending upon the route of administration and the preparationdesired. Standard texts, such as “REMINGTON′S PHARMACEUTICAL SCIENCE”,17th edition, 1985, incorporated herein by reference, may be consultedto prepare suitable preparations, without undue experimentation.

Various additives which enhance the stability and sterility of thecompositions, including antimicrobial preservatives, antioxidants,chelating agents, and buffers, can be added. Prevention of the action ofmicroorganisms can be ensured by various antibacterial and antifungalagents, for example, parabens, chlorobutanol, phenol, sorbic acid, andthe like. Prolonged absorption of the injectable pharmaceutical form canbe brought about by the use of agents delaying absorption, for example,aluminum monostearate and gelatin. According to the present invention,however, any vehicle, diluent, or additive used would have to becompatible with the cells or agents present in their conditioned media.

The compositions can be isotonic, i.e., they can have the same osmoticpressure as blood and lacrimal fluid. The desired isotonicity of thecompositions of this invention may be accomplished using sodiumchloride, or other pharmaceutically acceptable agents such as dextrose,boric acid, sodium tartrate, propylene glycol or other inorganic ororganic solutes. Sodium chloride is preferred particularly for bufferscontaining sodium ions.

Viscosity of the compositions, if desired, can be maintained at theselected level using a pharmaceutically acceptable thickening agent,such as methylcellulose. Other suitable thickening agents include, forexample, xanthan gum, carboxymethyl cellulose, hydroxypropyl cellulose,carbomer, and the like. The choice of suitable carriers and otheradditives will depend on the exact route of administration and thenature of the particular dosage form, e.g., liquid dosage form (e.g.,whether the composition is to be formulated into a solution, asuspension, gel or another liquid form, such as a time release form orliquid-filled form). Those skilled in the art will recognize that thecomponents of the compositions should be selected to be chemicallyinert.

Compositions comprising secreted cellular factors present in conditionedmedia (e.g., from the culture of epicardial progenitor cells and/orepicardial progenitor derived mesenchymal cells) are also administeredin an amount required to achieve a therapeutic or prophylactic effect.Such an amount will vary depending on the conditions of the culture.Typically, biologically active cellular factors present in theconditioned media will be purified and subsequently concentrated so thatthe protein content of the composition is increased by at least about5-fold, 10-fold or 20-fold over the amount or protein originally presentin the media. In other embodiments, the protein content is increased byat least about 25-fold, 30-fold, 40-fold or even by 50-fold. Preferably,the composition comprises an effective amount of a cellular factorisolated from an epicardial progenitor cell and/or an epicardialprogenitor derived mesenchymal cell.

The precise determination of what would be considered an effective doseis based on factors individual to each subject, including their size,age, sex, weight, and condition of the particular subject. Dosages canbe readily ascertained by those skilled in the art from this disclosureand the knowledge in the art.

Optionally, the methods of the invention provide for the administrationof a composition of the invention to a suitable animal model to identifythe dosage of the composition(s), concentration of components thereinand timing of administering the composition(s), which elicit tissuerepair, reduce cell death, or induce another desirable biologicalresponse. Such determinations do not require undue experimentation, butare routine and can be ascertained without undue experimentation.

Methods of Delivery

Compositions comprising one or more cellular factors (e.g., HGF VEGFSDF-1 alpha and IGF-1) present in conditioned media (e.g., agentsisolated from a culture of epicardial progenitor cells selected forexpression of epicardin, Nkx 2.5, GATA 4, Mef2c, and/or myocardin areprovided systemically or directly to a desired site (e.g., a site oftissue damage or ischemic injury). Modes of administration includeintramuscular, intra-cardiac, oral, rectal, topical, intraocular,buccal, intravaginal, intracisternal, intra-arterial,intracerebroventricular, intratracheal, nasal, transdermal, within/onimplants, e.g., fibers such as collagen, osmotic pumps, or parenteralroutes. The term “parenteral” includes subcutaneous, intravenous,intramuscular, intraperitoneal, intragonadal or infusion.

The isolated cellular factors can be administered via localizedinjection, including catheter administration, systemic injection,localized injection, intravenous injection, or parenteraladministration. When administering a therapeutic composition of thepresent invention, it will generally be formulated in a unit dosageinjectable form (solution, suspension, emulsion). Dosages can be readilyadjusted by those skilled in the art (e.g., a decrease in purity mayrequire an increase in dosage). Compositions of the invention can beintroduced by injection, catheter, or the like. Compositions of theinvention include pharmaceutical compositions comprising cellularfactors of the invention and a pharmaceutically acceptable carrier.Administration can be autologous or heterologous. For example,epicardial progenitor cells selected for expression of epicardin, Nkx2.5, Isl-1, GATA 5, WT1, Tbx18, and Tbx5 can be obtained from onesubject, and the CdM from the culture of such cells administered to thesame subject or a different, compatible subject.

If desired, biologically active agents present in conditioned media areincorporated into a polymer scaffold to promote tissue repair, cellsurvival, proliferation in a tissue in need thereof. Polymer scaffoldscan comprise, for example, a porous, non-woven array of fibers. Thepolymer scaffold can be shaped to maximize surface area, to allowadequate diffusion of nutrients and growth factors to a cell of theinvention. Polymer scaffolds can comprise a fibrillar structure. Thefibers can be round, scalloped, flattened, star-shaped, solitary orentwined with other fibers. Branching fibers can be used, increasingsurface area proportionately to volume.

Unless otherwise specified, the term “polymer” includes polymers andmonomers that can be polymerized or adhered to form an integral unit.The polymer can be non-biodegradable or biodegradable, typically viahydrolysis or enzymatic cleavage. The term “biodegradable” refers tomaterials that are bioresorbable and/or degrade and/or break down bymechanical degradation upon interaction with a physiological environmentinto components that are metabolizable or excretable, over a period oftime from minutes to three years, preferably less than one year, whilemaintaining the requisite structural integrity. As used in reference topolymers, the term “degrade” refers to cleavage of the polymer chain,such that the molecular weight stays approximately constant at theoligomer level and particles of polymer remain following degradation.

Materials suitable for polymer scaffold fabrication include polylacticacid (PLA), poly-L-lactic acid (PLLA), poly-D-lactic acid (PDLA),polyglycolide, polyglycolic acid (PGA), polylactide-co-glycolide (PLGA),polydioxanone, polygluconate, polylactic acid-polyethylene oxidecopolymers, modified cellulose, collagen, polyhydroxybutyrate,polyhydroxpriopionic acid, polyphosphoester, poly(alpha-hydroxy acid),polycaprolactone, polycarbonates, polyamides, polyanhydrides, polyaminoacids, polyorthoesters, polyacetals, polycyanoacrylates, degradableurethanes, aliphatic polyester polyacrylates, polymethacrylate, acylsubstituted cellulose acetates, non-degradable polyurethanes,polystyrenes, polyvinyl chloride, polyvinyl flouride, polyvinylimidazole, chlorosulphonated polyolifins, polyethylene oxide, polyvinylalcohol, teflon R™, nylon silicon, and shape memory materials, such aspoly(styrene-block-butadiene), polynorbornene, hydrogels, metallicalloys, and oligo(ε-caprolactone)diol as switchingsegment/oligo(p-dioxyanone)diol as physical crosslink. Other suitablepolymers can be obtained by reference to The Polymer Handbook, 3rdedition (Wiley, N.Y., 1989).

Screening Assays

The invention provides methods for identifying cellular factors presentin the conditioned media of a cell of the invention (e.g., an epicardialprogenitor cell selected for expression of epicardin, Nkx 2.5, Isl-1,GATA 5, WT1, Tbx18, and Tbx5). Such agents include proteins, peptides,polynucleotides, small molecules or other agents that enhance tissuerepair or increase cardiac function. Agents thus identified can be usedto enhance tissue repair by modulating, for example, the proliferation,survival, or differentiation of cells of the tissue of interest. In oneembodiment, agents identified according to a method of the inventionreduce apoptosis.

The test agents of the present invention can be obtained singly or usingany of numerous approaches. Such methods will typically involvecontacting a population of cells at risk of cell death with a test agentisolated from conditioned media and measuring an increase in survival ora reduction in cell death as a result of the contact. Comparison to anuntreated control can be concurrently assessed. Where an increase in thenumber of surviving cells or a reduction in cell death is detectedrelative to the control, the test agent is determined to have thedesired activity.

Fractionation of the conditioned media will be necessary to isolate oneor more cellular factors having a desired biological activity. Thus, thegoal of the extraction, fractionation, and purification process is thecareful characterization and identification of a chemical entity withinthe conditioned media having the desired biological activity. Methods offractionation and purification of heterogenous extracts are known in theart. If desired, peptides, polynucleic acids, or small compounds shownto be useful agents for enhancing tissue repair are chemically modifiedaccording to methods known in the art. Such agents may be characterizedfor biological activity in using methods known in the art, includinganimal models of tissue injury and disease (e.g., myocardial infarction,hind limb ischemia, and stroke).

Once identified, agents having a desired biological activity (e.g.,cardioprotective activity) may be recombinantly expressed and used tosupplement a therapeutic or prophylactic composition described herein(e.g., conditioned media).

Methods for Evaluating Therapeutic Efficacy

In one approach, the efficacy of the treatment is evaluated bymeasuring, for example, the biological function of the treated organ(e.g., cardiac cell function). Such methods are standard in the art andare described, for example, in the Textbook of Medical Physiology, Tenthedition, (Guyton et al., W.B. Saunders Co., 2000). In particular, amethod of the present invention, increases the biological function of atissue or organ by at least 5%, 10%, 20%, 40%, 50%, 60%, 70%, 80%, 90%,100%, 150%, 200%, or even by as much as 300%, 400%, or 500%. Preferably,the tissue is cardiac tissue and, preferably, the organ is heart.

In another approach, the therapeutic efficacy of the methods of theinvention is assayed by measuring an increase in cell number in thetreated or transplanted tissue or organ as compared to a correspondingcontrol tissue or organ (e.g., a tissue or organ that did not receivetreatment). Preferably, cell number in a tissue or organ is increased byat least 5%, 10%, 20%, 40%, 60%, 80%, 100%, 150%, or 200% relative to acorresponding tissue or organ. Methods for assaying cell proliferationare known to the skilled artisan and are described, for example, inBonifacino et al., (Current Protocols in Cell Biology Loose-leaf, JohnWiley and Sons, Inc., San Francisco, Calif.). For example, assays forcell proliferation may involve the measurement of DNA synthesis duringcell replication. In one embodiment, DNA synthesis is detected usinglabeled DNA precursors, such as [³H]-Thymidine or5-bromo-2*-deoxyuridine [BrdU], which are added to cells (or animals)and then the incorporation of these precursors into genomic DNA duringthe S phase of the cell cycle (replication) is detected (Ruefli-Brasseet al., Science 302(5650):1581-4, 2003; Gu et al., Science 302(5644):445-9, 2003).

In another approach, efficacy is measured by detecting an increase inthe number of viable cells present in a tissue or organ relative to thenumber present in an untreated control tissue or organ, or the numberpresent prior to treatment. Assays for measuring cell viability areknown in the art, and are described, for example, by Crouch et al. (J.Immunol. Meth. 160, 81-8); Kangas et al. (Med. Biol.62, 338-43, 1984);Lundin et al., (Meth. Enzymol.133, 27-42, 1986); Petty et al.(Comparison of J. Biolum. Chemilum.10, 29-34, 1995); and Cree et al.(AntiCancer Drugs 6: 398-404, 1995). Cell viability can be assayed usinga variety of methods, including MTT(3-(4,5-dimethylthiazolyl)-2,5-diphenyltetrazolium bromide) (Barltrop,Bioorg. & Med. Chem. Lett.1: 611, 1991; Cory et al., Cancer Comm. 3,207-12, 1991; Paull J. Heterocyclic Chem. 25, 911, 1988). Assays forcell viability are also available commercially. These assays include butare not limited to CELLTITER-GLO® Luminescent Cell Viability Assay(Promega), which uses luciferase technology to detect ATP and quantifythe health or number of cells in culture, and the CellTiter-Glo®Luminescent Cell Viability Assay, which is a lactate dehyrodgenase (LDH)cytotoxicity assay (Promega).

Alternatively, or in addition, therapeutic efficacy is assessed bymeauring a reduction in apoptosis. Apoptotic cells are characterized bycharacteristic morphological changes, including chromatin condensation,cell shrinkage and membrane blebbing, which can be clearly observedusing light microscopy. The biochemical features of apoptosis includeDNA fragmentation, protein cleavage at specific locations, increasedmitochondrial membrane permeability, and the appearance ofphosphatidylserine on the cell membrane surface. Assays for apoptosisare known in the art. Exemplary assays include TUNEL (Terminaldeoxynucleotidyl Transferase Biotin-dUTP Nick End Labeling) assays,caspase activity (specifically caspase-3) assays, and assays forfas-ligand and annexin V. Commercially available products for detectingapoptosis include, for example, Apo-ONE® Homogeneous Caspase-3/7 Assay,FragEL TUNEL kit (ONCOGENE RESEARCH PRODUCTS, San Diego, Calif.), theApoBrdU DNA Fragmentation Assay (BIOVISION, Mountain View, Calif.), andthe Quick Apoptotic DNA Ladder Detection Kit (BIOVISION, Mountain View,Calif.).

Methods for Evaluating Cardiac Function

Compositions of the invention may be used to enhance cardiac function ina subject having reduced cardiac function. Methods for measuring thebiological function of the heart (e.g., contractile function) arestandard in the art and are described, for example, in the Textbook ofMedical Physiology, Tenth edition, (Guyton et al., W.B. Saunders Co.,2000). In the invention, cardiac function is increased by at least 5%,10%, 15%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, or even 100% relativeto the cardiac function present in a naturally-occurring, correspondingtissue or organ. Most advantageously, cardiac function is enhanced ordamage is reversed, such that the function is substantially normal(e.g., 85%, 90%, 95%, or 100% of the cardiac function of a healthycontrol subject). Reduced cardiac function may result from conditionssuch as cardiac hypertrophy, reduced systolic function, reduceddiastolic function, maladaptive hypertrophy, heart failure withpreserved systolic function, diastolic heart failure, hypertensive heartdisease, aortic and mitral valve disease, pulmonary valve disease,hypertrophic cardiomyopathy (e.g., hypertrophic cardiomyopathyoriginating from a genetic or a secondary cause), post ischemic andpost-infarction cardiac remodeling and cardiac failure.

Any number of standard methods are available for assaying cardiovascularfunction. Preferably, cardiovascular function in a subject (e.g., ahuman) is assessed using non-invasive means, such as measuring netcardiac ejection (ejection fraction, fractional shortening, andventricular end-systolic volume) by an imaging method suchechocardiography, nuclear or radiocontrast ventriculography, or magneticresonance imaging, and systolic tissue velocity as measured by tissueDoppler imaging. Systolic contractility can also be measurednon-invasively using blood pressure measurements combined withassessment of heart outflow (to assess power), or with volumes (toassess peak muscle stiffening). Measures of cardiovascular diastolicfunction include ventricular compliance, which is typically measured bythe simultaneous measurement of pressure and volume, early diastolicleft ventricular filling rate and relaxation rate (can be assessed fromechoDoppler measurements). Other measures of cardiac function includemyocardial contractility, resting stroke volume, resting heart rate,resting cardiac index (cardiac output per unit of time [L/minute],measured while seated and divided by body surface area [m²])) totalaerobic capacity, cardiovascular performance during exercise, peakexercise capacity, peak oxygen (O₂) consumption, or by any other methodknown in the art or described herein. Measures of vascular functioninclude determination of total ventricular afterload, which depends on anumber of factors, including peripheral vascular resistance, aorticimpedance, arterial compliance, wave reflections, and aortic pulse wavevelocity, Methods for assaying cardiovascular function include any oneor more of the following: Doppler echocardiography, 2-dimensionalecho-Doppler imaging, pulse-wave Doppler, continuous wave Doppler,oscillometric arm cuff, tissue Doppler imaging, cardiac catheterization,magnetic resonance imaging, positron emission tomography, chest X-ray, Xray contrast ventriculography, nuclear imaging ventriculography,computed tomography imaging, rapid spiral computerized tomographicimaging, 3-D echocardiography, invasive cardiac pressures, invasivecardiac flows, invasive cardiac pressure-volume loops (conductancecatheter), non-invasive cardiac pressure-volume loops.

Kits

Compositions comprising a cell of the invention (e.g., an epicardialprogenitor cell selected for expression of epicardin, Nkx 2.5, Isl-1,GATA 5, WT1, Tbx18, and Tbx5) or a composition comprising biologicallyactive agents (e.g., HGF VEGF SDF-1 alpha and IGF-1) present inconditioned media of such cells is supplied along with additionalreagents in a kit. The kits can include instructions for the treatmentregime, reagents, equipment (test tubes, reaction vessels, needles,syringes, etc.) and standards for calibrating or conducting thetreatment. The instructions provided in a kit according to the inventionmay be directed to suitable operational parameters in the form of alabel or a separate insert. Optionally, the kit may further comprise astandard or control information so that the test sample can be comparedwith the control information standard to determine if whether aconsistent result is achieved.

The practice of the present invention employs, unless otherwiseindicated, conventional techniques of molecular biology (includingrecombinant techniques), microbiology, cell biology, biochemistry andimmunology, which are well within the purview of the skilled artisan.Such techniques are explained fully in the literature, such as,“Molecular Cloning: A Laboratory Manual”, second edition (Sambrook,1989); “Oligonucleotide Synthesis” (Gait, 1984); “Animal Cell Culture”(Freshney, 1987); “Methods in Enzymology” “Handbook of ExperimentalImmunology” (Weir, 1996); “Gene Transfer Vectors for Mammalian Cells”(Miller and Calos, 1987); “Current Protocols in Molecular Biology”(Ausubel, 1987); “PCR: The Polymerase Chain Reaction”, (Mullis, 1994);“Current Protocols in Immunology” (Coligan, 1991). These techniques areapplicable to the production of the polynucleotides and polypeptides ofthe invention, and, as such, may be considered in making and practicingthe invention. Particularly useful techniques for particular embodimentswill be discussed in the sections that follow.

The following examples are put forth so as to provide those of ordinaryskill in the art with a complete disclosure and description of how tomake and use the assay, screening, and therapeutic methods of theinvention, and are not intended to limit the scope of what the inventorsregard as their invention.

EXAMPLES Example 1 Isolated Cardiac Progenitor Cells are Capable ofEpithelial to Mesenchymal Transformation when Expanded in ConditionedMedia

Adult human atrial stem/progenitor cells were isolated from right atrialbiopsies. The right atrial appendage, commonly removed to install acardiopulmonary pump during bypass surgery, provided ample material toisolate atrial stem/progenitor cells from 11 out of 12 donors. Adulthuman atrial stem/progenitor cells were successfully isolated from 12out of 13 donors (Table 1).

TABLE 1 Patient Data for Epicardial Progenitor Cell Isolations. Sex AgeHTN DM CAD MR AS LVEF M 47 + + + − − 0.45 M 59 + − + − − NI M 57 − − + −− NI M 52 − − − + − NI M 57 − − + − − NI F 53 + − + − − NI M 80 + − −− + NI F 72 + − − + − 0.45 M 53 + + + − − NI M 78 − − + − − NI F 72 +− + − − NI F 60 + − + − − NI Abbreviations: HTN, hypertension; DM,diabetes mellitus; CAD, coronary artery disease; MR, mitralregurgitation; AS, aortic stenosis; LVEF, left ventricular ejectionfraction.

Right atrial appendages were obtained from consenting cardiac bypasspatients according to an Institutional Review Board (IRB) protocol thatwas approved by the University of Vermont (UVM). The appendages weretransferred from the hospital to the UVM Stem Cell Core on ice in 50 mlconical tubes containing explant medium: alpha MEM (Invitrogen,Carlsbad, Calif.), 10% fetal calf serum (FCS) (lot selected for rapidgrowth of hMSCs, Atlanta Biologicals, Lawrenceville, Ga.), 100 units/mlpenicillin, 100 μg/ml streptomycin, and 2 mM L-glutamine (MediatechInc., Hendron, Va.). In the cell culture hood, the tissue wasimmediately rinsed in phosphate buffered saline (1×PBS) and anyextracardiac fat was manually removed with fine scissors. The remainingtissue was transferred to a 100 cm² dish (Nunc, Thermo FisherScientific, Rochester, N.Y.) containing phosphate buffered saline(1×PBS) supplemented with 1 mg/mL collagenase/dispase (Roche AppliedScience, Indianapolis, Ind.). The tissue was minced into approximately 1mm³ pieces using sterile scalpel blades (#23, World PrecisionInstruments, Sarasota, Fla.). The dish was placed into a sterile 37° C.humidified cell culture incubator (Thermo Forma, 5% CO₂) for 1.5 hours,with shaking every 10 minutes. The resulting tissue digest was collectedand centrifuged at 600×g for 5 minutes. The pellet was resuspended andwashed in 25 mls of explant medium and centrifuged again. The finalpellet was resuspended in 20 ml of explant medium and the digestedfragments were split between 2 uncoated 100 cm² dishes. After 2-3 days,the dishes were supplemented by the addition of 5 ml of explant mediumand then left undisturbed to allow for the adherence of tissuefragments. Following 5-7 days, when fibroblast/endothelial outgrowthfrom the explants had almost reached confluence, the dishes were washedonce with phosphate buffered saline (1×PBS) and the explant medium waschanged to a medium that favored stem/progenitor cell growth: DMEM/F12(Invitrogen) with 3% FCS (Atlanta Biologicals) and 20 ng/ml epidermalgrowth factor (EGF), 10 ng/ml basic fibroblast growth factor (bFGF), 10ng/ml leukocyte migration inhibitory factor (LIF) (all growth factorsfrom Sigma, Saint Louis, Mo.), 1× insulin, transferrin, selenium (ITSplus) (BD Biosciences, San Jose, Calif.), 100 units/ml penicillin, 100μg/ml streptomycin, and 2 mM L-glutamine (Mediatech Inc.). After 2-3days, areas of stem/progenitor cells were observed proliferating inbetween the fibroblasts/endothelial cells.

The stem/progenitor cells were distinguishable by morphology. They didnot mix with the other cells in the dishes, and formed spheroids and“bunches of grapes” as they divided upwards into the medium rather thanhorizontally. By shaking the dishes and washing once with calcium- andmagnesium-free PBS, the loose aggregates and spheroids ofstem/progenitor cells were collected, centrifuged at 600×g for 5minutes, resuspended in Claycomb expansion medium (SAFC Biosciences,Sigma) with 10% fetal calf serum (FCS), 100 units/ml penicillin, 100μg/ml streptomycin, and 2 mM L-glutamine, and transferred to new dishes.Following adherence to culture plastic, the majority of the atrialstem/progenitor cells underwent epithelial to mesenchymal transformation(EMT) into mesodermal progenitors and precursor cells as they expandedin the high serum medium.

The isolation method yielded relatively pure cultures of proliferatingepicardial progenitor cells that expressed markers of epicardial andcardiac stem/progenitor cells such as epicardin, Nkx 2.5, Isl-1, GATA 5,WT1, Tbx18, and Tbx5 (FIGS. 1A-1L). The epicardial stem/progenitor cellscould be maintained as undifferentiated epithelial cultures on uncoatedpolystyrene dishes in stem/progenitor cell medium (FIG. 1C) or could bemade to undergo EMT into mixtures of transit-amplifying precursor cellsafter plating onto charged or coated cell ware in medium containing 10%fetal calf serum (FIG. 1D). The expression levels of mRNAs for severaltranscription factors decreased as the cells differentiated (see GATA5,WT1, Isl-1, and Tbx18; FIG. 1K). In contrast, the expression levels ofmRNAs for smooth muscle actin and von Willebrand Factor (vWF) increasedfrom low or undetectable levels in undifferentiated epicardialstem/progenitor cells to readily detectable levels as the cellsdifferentiated into precursor cells (FIG. 1K). In addition, theprecursor cells expressed the mRNAs of upstream transcription factorssuch as GATA4, Mef2c, and Myocardin (FIG. 1L).

An alternative method was also developed (method#2) by direct culture ofhuman epicardium dissected from the surface of right atrial appendages,which produced proliferating epicardial progenitor-like cells like thoseobtained using the method above (method#1).

The epicardial progenitor cells were maintained as epithelial culturesin stem/progenitor cell medium or were induced to undergo epithelial tomesenchymal transformation into mixtures of transit-amplifying precursorcells following adherence to culture plastic. After plating onto chargedor coated cell ware in medium containing 10% fetal calf serum (FCS), themajority of the atrial stem/progenitor cells underwent epithelial tomesenchymal transformation into mesodermal progenitors and precursorcells as they expanded in the high serum medium. Some of the precursorcells expressed contractile proteins characteristic of myocytes, whileothers expressed markers of smooth muscle cells or endothelial cells(FIGS. 2A-2M). The gap junction proteins Cx40 and Cx43 were expressed bythe atrial precursor cells, as well as the calcium handling proteinCalsequestrin and the SERCA2a ATPase (FIGS. 2E-2H).

Cell surface phenotyping demonstrated that multiple cell surfaceantigens typical of bone marrow MSCs such as CD105, CD90, CD73, CD54,CD49d, CD44, and CD29 were expressed by the EDPCs (FIGS. 3A and 3B).However, the precursor cells were negative for endothelial andhematopoietic cell surface markers such as CD31, CD34, CD45, and c-kit,and also the vascular pericyte marker NG2. Many of the precursor cellsexpressed cell surface antigens typical of mesenchymal stem cells(MSCs), such as CD105, CD90, CD73, CD44, CD29 and Stro-1 (FIG. 3A). Cellsurface phenotyping showed that EDPCs generated by methods #1 and #2expressed identical antigen profiles (FIGS. 3A and 3B).

In an attempt to replace cardiac cells after myocardial infarction,epicardial precursor cells cultured for 2 passages were administered to3 different strains of immunodeficient mice (NOD/SCID, NOD/SCID/beta 2m^(−/−), NOD/SCID/IL2rγ^(−/−)) by either intramuscular injection intoborder zone areas or by intra-arterial (left ventricle lumen)administration 1 day after myocardial infarction. The intramuscular cellinjections were associated with a persistent but low level of human cellengraftment in the left ventricle (LV) wall 1 week after injection. Theintra-arterial infusion of cells after myocardial infarction (MI) led tomicro vascular emboli and sudden cardiac death.

Example 2 Conditioned Media Produced from Epicardial Progenitor CellsPreserved Cardiac Function after Myocardial Infarction

In cardiac development epicardial cells provide supportive andmultifaceted roles. To determine whether agents present in conditionedmedia secreted by expanded epicardial precursor cells could providecardioprotection or promote cardiac regeneration after myocardialinfarction, a mouse model of myocardial infarction (MI) was used. Due tothe human origin of the epicardial progenitor cells, immunodeficient(NOD/SCID) mice were used for treatment with CdM.

To prepare conditioned media from human atrial progenitor cells, atrialprogenitor cells cultured for 3 passages were grown in Claycombexpansion medium on 150 cm² dishes (Nunc). When the cells reached 70-90%confluence, the plates were washed twice with PBS and serum-free alphaminimal essential media (MEM) was placed on the cells (20 mls perplate). After 48 hours of incubation, the conditioned media wascollected, filtered (0.2 μm PES membrane, Nalgene MF75, Rochester,N.Y.), and concentrated 30-fold with a commercially availablediafiltration system (Labscale™ TFF diafiltration system) using filterswith a 5 kD cut-off (Millipore, Bedford, Mass.). Medium components above5 kD were concentrated (base medium components and salts remained at1×). One ml vials of conditioned media were frozen and stored at −80° C.

Groups of immunodeficient (NOD-SCID) and immunocompetent (C57 Bl6/J)mice underwent coronary ligation surgery during which the ligatureremained in place for 4 hours. Following recovery of the animal afterinitial suture placement, the mouse was again anesthetized, intubated,and surgically opened at 4 hours post-ligation. Once the intact sutureand area of blanching were confirmed and reperfusion was accomplished,Human EPI CdM (30×, 200 μl) warmed to 37° C. was delivered to the entirecardiovascular arterial tree by injecting the solution into the lumen ofthe left ventricle (LV). This method was designed to deliver a maximumamount of conditioned media to the injured myocardium by employing thenaturally existing arterial network of the heart, which is supplied bythe immediate portion of the aorta. Using a 30.5 gauge needle insertedbelow the great cardiac vein (LV apex) at an angle 45° to themyocardium, 200 μl of 30× conditioned media warmed to 37° C. was slowlyinjected over a period of 1 minute. Control animals received AlphaMinimum Essential Medium (vehicle control, 200 μl) in the same manner.All animals were randomized to treatment at the end of the first surgery(after ligation) and prior to revascularization. Following treatmentwith either conditioned media or vehicle, the needle was removed and theintercostals were rejoined using 6.0 chromic gut suture (Ethicon,Johnson and Johnson, Inc., Livingston, UK). The lungs reinflated, andthe overlying dermis was rejoined with 6.0 nylon suture. Sham miceunderwent all procedures except that the suture was passed under theleft anterior descending coronary artery (LAD) and not tied. All micewere then recovered to an ambulatory state and transferred to thevivarium for the remaining duration of the experiment.

At 1 week after myocardial infarction, dramatic improvements in cardiacfunction were observed by echocardiography (ECHO) in conditionedmedia-treated mice compared with controls that received vehicleinfusion. There was a highly significant difference in both thepercentage of fractional shortening and anterior wall thickness duringsystole and diastole for immunodeficient mice treated with conditionedmedia compared with controls (percent fractional shortening (FS),p≦0.001; AWT (S-D), p≦0.001; FIGS. 4A-4C). ECHO scores were determinedby a blinded observer using a 13 segment model similar to the AmericanSociety of Echocardiography's 17 segment model. ECHO scores demonstratedpreservation of wall motion in conditioned media-treated mice comparedwith controls (p≦0.01, FIG. 4C). Conditioned media from human atrialprogenitor cells improved cardiac function in immunodeficient mice aftermyocardial infarction with reperfusion.

Assessment of surviving ventricular myocardium after myocardialinfarction by creatine kinase (CK) activity assays demonstrated aprofound rescue of cardiac tissue and a highly significant decrease inthe percentage of myocardial infarction in the CdM treatment group(FIGS. 5A and 5B). According to an algorithm that correlated the levelof creatine kinase activity with the percentage of myocardium withinfarction, the conditioned media treatment reduced the myocardialinfarction in the left ventricle walls of immunodeficient mice by about50% (FIGS. 5A and 5B).

The conditioned media from the human epicardial progenitor cells alsorescued left ventricular myocardium in immunocompetent mice.Representative M Mode images and electrocardiograms (ECG) forsham-operated, conditioned media-treated, and alpha MEM-treated(control) mice are shown in FIGS. 6A-6C. There was a significantincrease in the percentage of fractional shortening in conditionedmedia-treated immunocompetent mice compared with controls, in anteriorwall thickness between systole and diastole, and in wall motion asdetermined again by ECHO scoring (percent FS, p≦0.01; AWT (S-D), p≦0.01;ECHO score, p≦0.001; FIGS. 7A-7C). The percent FS for sham-operated andCdM-treated mice was not significantly different (p=0.448). There weresignificant improvements in left ventricular dimensions during bothsystole and diastole in conditioned media-treated versus control animals(LVESD, p≦0.01, LVEDD, p≦0.05; FIGS. 8A and 8B). For immunocompetentmice with myocardial infarction, there was a highly significant increasein cardiac output as measured from the pulmonary artery in theconditioned media-treated group compared with controls (p≦0.0001, FIG.9). In fact, cardiac output after myocardial infarction for conditionedmedia-treated mice did not differ from that of sham-operated mice(p=0.807). Similar to the case in NODSCID mice, the EPI CdM treatmentreduced the extent of infarction in C57bl6/J mice by over 50% (FIGS.10A-10C). Gomori trichrome staining of serial sections from control andEPI CdM-treated mice at 7 days after MI demonstrated that EPI CdMtreatment decreased the area of tissue injury (FIG. 10A). By creatinekinase assays the epicardial progenitor cell conditioned media reducedthe percentage of left ventricle with myocardial infarction inimmunocompetent mice by over 50% (FIGS. 10B and 10C). To determinewhether EPI CdM treatment could provide long-term benefit, groups ofC57bl6/J mice were observed for 1 month after MI, reperfusion andtreatment to evaluate their cardiac function. Significant differences incardiac function between EPI CdM-treated mice and controls were stillevident at 1 month after treatment (FIGS. 10D-10F).

Example 3 Conditioned Media from the Human Epicardial Progenitor CellsContains Growth Factors that Reduce Cardiac Necrosis FollowingMyocardial Infarction

To examine the timing and nature of cardioprotection provided byconditioned media from the human epicardial progenitor cells (EPI CdM),groups of immunocompetent mice were subjected to the 4 hourischemia/reperfusion myocardial infarction (MI) model, treated with EPICdM at the time of reperfusion, and euthanized after 24 hours todetermine the numbers of cardiac cells undergoing apoptosis or necrosis.Similar to the results reported above, immunohistochemical assaysspecific for apoptotic cells (single-stranded DNA, ssDNA) minimalnumbers of apoptotic cells were observed in either control hearts orthose treated with EPI CdM at 24 hours after ischemia and reperfusion(FIGS. 12A-12G). Because one apoptotic cell was detected(ssDNA-positive) or less on multiple heart sections from control and EPICdM-treated animals, apoptosis was not quantified. In contrast, TUNELstaining of control hearts that received alpha MEM infusion indicatedwidespread cardiac necrosis at 24 hours after MI (FIGS. 12C and D). EPICdM treatment significantly reduced the numbers of TUNEL-positive cellswithin the infarct zone at 24 hrs after MI (P=0.023, FIG. 12E-G).

To characterize the cardioprotective factors contained in EPI CdM,ELISAs for Hepatocyte Growth Factor (HGF), Vascular Endothelial GrowthFactor (VEGF), Insulin-like Growth Factor (IGF-1), and Stromal-DerivedFactor 1 (SDF-1 alpha) were performed on EPI CdM (FIGS. 13A and 14). EPICdM examined from several different human donors contained relativelyhigh levels of HGF (about 3 ng/ml in 1×EPI CdM, FIG. 13A), variablelevels of VEGF (between 500 pg/ml and 2.5 ng/ml, FIG. 14), and lowlevels of SDF-1 alpha (<150 pg/ml, FIG. 14) and IGF-1 (<30 pg/ml, FIG.14).

To examine whether EPI CdM from donors of varying ages would providecardioprotection, cell protection assays were performed under conditionsof simulated ischemia (low glucose medium, 1% oxygen, for 24 or 48 hrs).Compared with incubation in alpha MEM (vehicle), unconcentrated EPI CdMsgenerated from precursor cells of donors from 52 to 80 years of age allsignificantly protected primary human cardiac endothelial cells fromsimulated ischemic injury for 24 hours (FIG. 13B). EPI CdMs concentratedto 10× provided a greater level of cell protection than didunconcentrated 1×EPI CdMs and significantly protected both human aorticand coronary artery endothelial cells for 48 hours (FIGS. 13C-13F).Neutralizing antibodies to human HGF, but not VEGF, significantlyreduced EPI CdM-mediated protection of primary human aortic and coronaryartery endothelial cells (FIG. 13C-13F). Notably, advanced patient agedid not diminish the ability of EPI CdM to provide vaso- orcardioprotection. EPI CdM generated from EDPCs of an 80 yr old patientprotected cardiac endothelial cells as well as EPI CdM from a 50 yr oldpatient and preserved myocardial tissue in multiple mouse strains afterMI. Relevant to clinical application, the human EPI CdM we used wasproduced, sterile filtered, and stored frozen, consistent with a longshelf life.

To determine the relative importance of HGF in the cardioprotectionconferred by EPI CdM in vivo, pulldowns (PD) were performed withbiotinylated antisera specific to HGF or biotinylated nonspecific IgG(control). By ELISA, incubation in strepavidin-agarose andcentrifugation removed 100% of HGF from EPI CdM (FIG. 15). Groups ofC57bl6/J mice were subjected to the 4 hr ischemia/reperfusion MI model,and were treated with Alpha MEM, nonspecific IgG-PD EPI CdM (IgG-PD), orHGF-PD EPI CdM (HGF-PD). Removal of HGF from EPI CdM significantlyreduced its therapeutic effects as determined by several criteria usedto assess cardiac function (FIGS. 13G-13I) and the degree of tissuepreserved at 1 wk after MI, reperfusion and treatment (FIGS. 13K and13L). Assay of residual LV CK showed that treatment with HGF-PD resultedin a 51% decrease in the amount of cardiac muscle rescued by IgG-PDtreatment. Notably, however, the removal of HGF only partially reducedthe beneficial effects of EPI CdM. Treatment with HGF-PD still providedsignificant improvement in cardiac function compared with AlphaMEM-infused controls (FIGS. 13A-13L). In addition, the cardiac output ofmice that received HGF-PD did not differ from that of IgG-PD treatedmice (FIG. 13J).

Example 4 EPI CdM Preserves Cardiac Tissue after MI in a Large AnimalModel (Swine)

To determine whether human EPI CdM would also preserve cardiac tissueafter MI in a large animal model, studies with 10 adult conventionalfarm swine were carried out (˜65 kgs). Under anesthesia and withfluoroscopic guidance, a balloon catheter was advanced and inflated tocompletely occlude the LAD for 1 hour prior to revascularization. At thetime of reperfusion, pigs in the control group received additionalcontrast dye to confirm re-flow (n=5). Alternatively, pigs in thetreatment groups received 16 mls of 20×EPI CdM and contrast (n=3) or 16mls of 25×EPI CdM and contrast (n=2), by infusing 8 mls of EPI CdMdirectly into the LCAD at the location of the deflated balloon, and anadditional 8 mls into the left main coronary artery from the guidecatheter. The EPI CdM was infused over 3-5 minutes. No anti-arrhythmicdrugs were used and there were no adverse events following any of thetreatments. All pigs were euthanized at 24 hours after treatment. Thehearts were removed and cut transversely from apex to base (1 cmslices), stained by 2,3,5-Triphenyltetrazolium chloride (TTC), anddigitally photographed (FIG. 16A). The weights of right and leftventricular tissue from each 1 cm slice were recorded. The areas ofviable and scarred cardiac tissue were quantified with Scion Imagesoftware, averaged between slices, and multiplied by the tissue weightsto estimate infarct size. As the effects of 20× and 25×EPI CdM oninfarct size were similar (both P=0.03 compared with control infarctsize), the treatment data was grouped together (FIGS. 16A-16C). Thecombined data indicated a 51% reduction in infarct size at 24 hoursafter MI compared with infarct size in controls that received contrastalone (P=0.024, FIG. 16B). However, by gross inspection hearts treatedwith 25×EPI CdM appeared better than those treated with 20×EPI CdM, withislands of spared (viable) myocardium at the apex (FIG. 16C).

Example 5 EPI CdM Provides Vasoprotection and Prevents Vascular Rhexisafter MI and Reperfusion

To determine whether EPI CdM treatment was vasoprotective in the contextof MI and reperfusion, assays of vascular integrity were performed at 24hrs after MI, reperfusion and treatment. As HGF depletion only partiallyreduced the benefit of EPI CdM treatment, multiple factors present inEPI CdM could work in concert to preserve vascular integrity after MIand reperfusion. Using the same biotinylated antibody PD strategy toremove multiple growth factors simultaneously, HGF, VEGFA, and SDF-1alpha were depleted from 30×EPI CdM (3 GF PD). Non-specific IgG-PDcontrol EPI CdM was formulated to match the concentrations of IgG usedfor specific PD.

To assess microvascular rhexis, FITC-albumin (FITC-Alb) was injected bytail vein 2 hrs before euthanization. Serial sections were cut from eachheart from apex to base and used to determine the mural volumecontaining extravasated FITC-Alb. TUNEL assays performed on the samesections demonstrated that FITC-positive areas of the LV correlated withareas of cellular necrosis (FIGS. 17A-17D and 18; Table 2).

TABLE 2 Correlation of TUNEL positive cells in left ventricle with areascontaining FITC-Alb at 24 hr after MI and reperfusion Outside BorderInside (%) (%) (%) Alpha MEM A 0 0 100 B 0 0 100 C 0 0 100 D 25 0 100IgG-PD A 16.7 40 100 B 0 50 100 C 0 0 100 D 0 0 100 E 0 25 100 F 0 33.3100 3 GF PD A 33.3 33.3 100 B 0 20 100 C 0 0 100 D 0 25 100 E 0 0 100Serial sections spanning the infarct zone were scored for presence orabsence of TUNEL positive cells outside the FITC-positive area, inborder regions of FITC staining, and inside the FITC-positive area.Border regions were defined by taking photomicrographs that contained50% of FITC-positive myocytes and 50% FITC-negative myocytes. Dataindicate the percentage of sections that contained at least a singleTUNEL-positive cell in a particular area for a given animal. For eachanimal, 4 to 5 sections were scored that spanned the region ofinfarction.

Compared with Alpha MEM treatment, IgG-PD treatment significantlyreduced the LV mural volume of FITC-Alb, indicating that EPI CdMtreatment protects against vascular rhexis that occurs after reperfusion(FIGS. 17E and 17F). By contrast, 3 GF PD treatment did not protectagainst vascular rhexis. In fact, the LV volume containing FITC-Alb inmice that received 3 GF PD did not differ from that of Alpha MEM-treatedcontrols (FIGS. 17E and 17F).

For an independent measure of vascular rhexis, blood serum samplesobtained from the same mice at 24 hrs after reperfusion were assayed forthe long pentraxin, PTX3, a marker of inflammation and vasculopathyafter MI²⁹. PTX3 expression increases in neutrophils, macrophages andendothelial cells after MI and is released by damaged/dying endothelialcells within hours of reperfusion following myocardial ischemia²⁹.

By ELISA, serum PTX3 levels increased markedly at 24 hrs afterreperfusion in Alpha MEM control animals compared with sham-operatedmice that had suture passed under the LAD but were not ligated (FIG.17F). In agreement with the FITC-Alb data, serum PTX3 was significantlyreduced in mice that had been treated with IgG-PD. Similarly,concentrations of PTX3 in serum of mice treated with 3 GF PD did notdiffer from those in Alpha MEM controls (FIG. 17F). Taken together,these data indicate that multiple factors present in EPI CdM act rapidlyand in synergy to reduce cardiac necrosis and infarct expansion bypreventing the progression of vascular rhexis³⁰ after reperfusion.

In patients with acute MI, concentrations of PTX3 in blood predictmortality³¹. Therefore, the results with PTX3 are consistent with anovel and clinically relevant approach of putative value for treatmentafter MI based on human EPI CdM or its ligands. Without intending to bebound to theory, EPI CdM treatment after MI prevents vascular rhexis,and permits reperfusion to salvage damaged cardiomyocytes throughmicrovasculature.

Most studies that treat animal models of acute MI with adultstem/progenitor cells^(6,32,33) or conditioned medium^(9,10,24) employ apersistent coronary ligation^(6,9,10,24,32,33), treat by intramuscularinjection^(6,9,10,24,32,33), and treat very early after MI (e.g.immediately^(6,24,32), 30 min⁹ or 1 ^(hr10,33) after ligation). Thestudies described herein, were performed under clinical circumstance, inwhich a period of myocardial ischemia is followed by revascularization.Despite a relatively long 4 hr interval of ischemia, intra-arterialadministration of EPI CdM at the time of reperfusion was sufficient toprovide substantial preservation of cardiac tissue and function. Becauseof the small size of the murine heart, EPI CdM was injected into theleft ventriclular lumen for delivery into the coronary arterial bloodafter reperfusion. Without intending to be bound to theory, one maydeliver EPI CdM or a defined combination of its ligands (withstabilizing carriers such as albumin) directly into coronary arteries atthe time of percutaneous coronary intervention to obtain benefits inpatients. Recently, CdM from porcine bone marrow MSCs was deliveredthrough an intracoronary infusion catheter after 60 min of myocardialischemia in pigs³⁴.

Without intending to be bound to theory, EPI CdM treatment has thepotential to reduce the “no re-flow” phenomenon commonly observed afterreperfusion in animal models^(35,36) and in patients with MI³⁷. Nore-flow refers to compromised distal myocardial perfusion despiterestoration of patency in macroscopic vessels. After MI andrecanalization of an infarct-related artery, myocardial perfusion canbecome progressively impaired, despite relief of the coronaryocclusion³⁸. The extent of no re-flow is known to predict infarctexpansion³⁶ and the results herein indicate that EPI CdM treatmentrapidly reduces myocardial necrosis and infarct expansion after MI bypreventing the progression of vascular rhexis that occurs followingreperfusion.

The results described in the Examples above were obtained using thefollowing methods and materials.

Isolation of Adult Human Epicardial Progenitor-Like Cells and EMT intoPrecursor Cells

Right atrial appendages were obtained from consenting cardiac bypasspatients in a protocol that was approved by the IRB of the University ofVermont. The appendages were transferred from the hospital to the UVMStem Cell Core on ice in 50 ml conical tubes containing explant medium:Alpha MEM (Invitrogen, Carlsbad, Calif.), 10% FCS (lot selected forrapid growth of hMSCs, Atlanta Biologicals, Lawrenceville, Ga.), 100units/ml penicillin, 100 μg/ml streptomycin, and 2 mM L-glutamine(Mediatech Inc., Hendron, Va.).

Method #1

In a cell culture hood, appendages were immediately rinsed in 1×PBS andany extracardiac fat was manually removed with fine scissors. Theremaining tissue was transferred to a 100 cm² dish (Nunc, Thermo FisherScientific, Rochester, N.Y.) containing 1×PBS supplemented with 1 mg/mLcollagenase/dispase (Roche Applied Science, Indianapolis, Ind.) in whichit was minced into approximately 1 mm³ pieces with sterile scalpelblades (#23, World Precision Instruments, Sarasota, Fla.). The dish wasplaced into a sterile 37° C. humidified cell culture incubator (ThermoForma, 5% CO₂) for 1.5 hours, with shaking every 10 minutes. Theresulting tissue digest was collected and centrifuged at 600×g for 5min. The pellet was resuspended and washed in 25 mls of explant mediumand centrifuged again. The final pellet was resuspended in 20 mls ofexplant medium and the digested fragments were split between 2 uncoated100 cm² dishes. After 2-3 days, the dishes were supplemented by theaddition of 5 mls of explant medium and then left undisturbed to allowfor the adherence of tissue fragments.

After 5-7 days, when fibroblast outgrowth from the explants had nearlyreached confluence, the dishes were washed once by PBS and the explantmedium was changed to a medium that favored stem/progenitor cell growth:DMEM/F12 (Invitrogen) with 3% FCS (Atlanta Biologicals) and 20 ng/mlEGF, 10 ng/ml bFGF, 10 ng/ml LIF (all growth factors from Sigma, SaintLouis, Mo.), 1×ITS plus (BD Biosciences, San Jose, Calif.), 100 units/mlpenicillin, 100 μg/ml streptomycin, and 2 mM L-glutamine (MediatechInc.).

After 2-3 days, areas of epicardial progenitor cells were observedproliferating in between the fibroblasts. The progenitor cells weremorphologically distinguishable from surrounding cell types, did not mixwith surrounding cells, and formed floating spheroids and cellaggregates that resembled bunches of grapes as they divided upwards intothe medium rather than horizontally. By shaking the dishes and washingonce with calcium- and magnesium-free PBS, the floating progenitor cellswere collected. The resulting cells (epicardial progenitor-like cells)were cultured in petri dishes (uncharged) in stem/progenitor growthmedium for up to several weeks (in some cases up to 2 months).

The epicardial nature of the cells was clear as all of the cells wereepithelial and expressed Keratin proteins. Under these conditions, theepithelial cells continued to produce floating cells. To induce EMT, theepicardial cells were collected, centrifuged at 600×g for 5 min,resuspended in Claycomb medium (SAFC Biosciences, Sigma) with 10% FCS,100 units/ml penicillin, 100 μg/ml streptomycin, and 2 mM L-glutamine,and transferred to new dishes. Following adherence to culture plastic,the majority of the progenitor-like cells underwent EMT within 3 daysinto precursor cells and expanded rapidly in the Claycomb medium with10% FCS.

Whether long-term growth in the stem/progenitor cell medium (low serumwith growth factors) and in uncoated petri dishes were important togenerate the precursor cells at the next stage of culture was examined.This was not the case as primary floating epithelial progenitor cellsobtained directly from initial the feeder layer cultures could alsoundergo EMT when plated onto typical positively-charged cell culturedishes and incubated in the Claycomb medium with 10% FCS. Furthermore,immunocytochemistry, cell surface phenotyping, and ELISA data indicatedthat the precursor cells derived from EMT did not differ whether thecells were rapidly induced to undergo EMT or were maintained for severalweeks as epithelial progenitor cells and then induced to undergo EMT.

Method #2

A faster method was developed involving isolating EDPCs by directculture of human epicardium dissected from the surface of right atrialappendages (FIGS. 1M-1P). Epicardial explants were cultured for up to 7days in explant medium to allow outgrowth of epithelial cells. Uponswitching to the adult stem/progenitor medium as above, the epithelialcells similarly became refractile and formed spheres and “bunches ofgrapes”. These progenitor-like cells also expressed Keratins and couldbe induced to undergo EMT into EDPCs in Claycomb medium containing 10%FCS (as above). Cell surface phenotyping showed that EDPCs generated bymethod#1 or method#2 expressed identical antigen profiles (forcomparison see, e.g., FIGS. 3A and 3B).

Immunocytochemistry and Immunohistochemistry

Atrial precursor cells were cultured for 2 days in Claycomb expansionmedium in Labtek chamber slides (Nunc). They were washed once with PBSand fixed by a 10 minute incubation in 4% paraformaldehyde in phosphatebuffered saline (PBS). Following several PBS washes, the chamber slideswere blocked for 1 hour with 5% goat serum with 0.4% Triton-X 100 inPBS. Primary antibodies were diluted into blocking solution, placed onthe cells, and incubated overnight at 4° C. (see below, antibody listand dilutions). Following 3×PBS washes, secondary antisera was appliedin blocking buffer and incubated for 1 hour at room temperature. After 3more washes, slides were mounted and coverslipped (Vectashield withDAPI, Vector laboratories, Burlingame, Calif.) and viewed with anepifluorescence microscope (Leica DM6000B with DFC350 FX camera). Doubleimmunohistochemistry was performed as in Spees et al. 2008 (FASEB J.April; 22(4):1226-36).

Primary Antisera:

Smooth muscle myosin heavy chain, SMMS-1, Dako, 1:100 Carpinteria, CAVon Willebrand Factor, F8/86, Dako 1:50 Human STRO-1, MAB1038, R and DSystems, Minneapolis,  5 μg/ml MN GATA 4, G-4, Santa Cruz Biotechnology,Santa Cruz, CA 1:100 Nkx 2.5, H-114, Santa Cruz 1:50 Cytokeratin(mixture), C2562, Sigma 1:100 Alpha smooth muscle actin, clone 1A4,A2547, Sigma 1:800 Sarcomeric actin, A2172, Sigma 1:500 SERCa2 ATPase,clone IID8, S1439, Sigma 1:400 Cardiac calsequestrin, C2491, Sigma 10μg/ml Connexin 43, C6219, Sigma 1:400 Connexin 40, 36-4900, ZymedLaboratories (Invitrogen)  2 μg/ml Epicardin (TCF21), ab32981, Abcam1:100 Myosin light chain phospho S20, ab2480, Abcam 1:100 Vimentin,E2944, Spring Bioscience, Freemont, CA 1:200Secondary Antisera:

Goat anti-mouse IgG ALEXA 594, Molecular Probes, Invitrogen 1:800 Goatanti-mouse IgG ALEXA 488, Molecular Probes, Invitrogen 1:500 Goatanti-mouse IgM ALEXA 594, Molecular Probes, Invitrogen 1:800 Goatanti-rabbit IgG ALEXA 594, Molecular Probes, Invitrogen 1:800 Goatanti-rabbit IgG ALEXA 488, Molecular Probes, Invitrogen 1:500 Donkeyanti-goat IgG ALEXA 594, Molecular Probes, Invitrogen 1:800Reverse Transcriptase Polymerase Chain Reaction (RT-PCR)

Total RNA was isolated from cell pellets using a commercial kit(RNAqueous, Ambion, Austin, Tex.). To avoid the possibility ofcontaminating DNA, the total RNA samples were treated with DNase priorto reverse transcription (TURBO DNase, Ambion). Reverse transcriptionwas performed with Superscript III (Invitrogen) in the presence of RNaseinhibitor (RNaseOUT, Invitrogen). PCR was carried out using an EppendorfMaster Cycler EP thermal cycler. Control RT-PCR reactions includedtemplate samples in which the reverse transcriptase was omitted from thesingle strand synthesis reaction. Primer sequences and annealingtemperatures are listed below. Target sequences were denatured at 94° C.(2 minutes) followed by 30 amplification cycles of 94° C. (30 seconds),anneal temp (30 seconds), and 72° C. (45 seconds). The last PCR stepextended the products at 72 C for 1 minute. RT-PCR products wereanalyzed on 1% agarose gels.

PCR Primers:

Tm ° C. Cardiac alpha actin Forward 5′ TGC TGA TCG TAT GCA GAA GG 3′(SEQ ID NO: 1) 54.8 Reverse 5′ GCT GGA AGG TGG ACA GAG AG 3′(SEQ ID NO: 2) 57.3 MLC4 Forward 5′ AAG ATC ACC TAC GGC CAG TG 3′(SEQ ID NO: 3) 56.8 Reverse 5′ CCC TCC ACG AAG TCC TCA TA 3′(SEQ ID NO: 4) 55.8 SERCA2a Forward 5′ GGT GCT GAA AAT CTC CTT GC 3′(SEQ ID NO: 5) 54.3 Reverse 5′ ATC AGT CAT GCA CAG GGT TG 3′(SEQ ID NO: 6) 55.3 MLC2a Forward 5′ GTC TTC CTC ACG CTC TTT GG 3′(SEQ ID NO: 7) 55.7 Reverse 5′ CCA CCT CAG CTG GAG AGA AC 3′(SEQ ID NO: 8) 57.3 MLC2v Forward 5′ GGT GCT GAA GGC TGA TTA CGT T 3′(SEQ ID NO: 9) 56.7 Reverse 5′ TAT TGG AAC ATG GCC TCT GGA T 3′(SEQ ID NO: 10) 56.1 GAPDH Forward 5′ GCT GAG TAC GTC GTG GAG T 3′(SEQ ID NO: 11) 56.6 Reverse 5′ CAC CAC TGA CAC GTT GGC A 3′(SEQ ID NO: 12) 58.3 Cx43 Forward 5′ AGG CGT GAG GAA AGT ACC AA 3′(SEQ ID NO: 13) 56.2 Reverse 5′ ACA CCT TCC CTC CAG CAG TT 3′(SEQ ID NO: 14) 58.7 Myocardin Forward 5′GGA CTG CTC TGG CAA CCC AGT GC 3′ (SEQ ID NO: 15) 64.7 Reverse 5′CAT CTG ACT CCG GGT CAT TTG C 3′ (SEQ ID NO: 16) 61.9 vWF Forward 5′AAG AAC CGA AGT CCC AGG AGA AAG (SEQ ID NO: 17) 61.5 G 3′ Reverse 5′AGA TTT CAG AGG CGT TCT AAA ACT (SEQ ID NO: 18) 58.4 CA 3′Smooth muscle alpha actin Forward 5′ GAA GAG GAC AGC ACT GCC T 3′(SEQ ID NO: 19) 57.1 Reverse 5′ CTG ATA GGA CAT TGT TAG CAT A 3′(SEQ ID NO: 20) 49.6 GATA4 Forward 5′ GAC GGG TCA CTA TCT GTG CAA C 3′(SEQ ID NO: 21) 57.8 Reverse 5′ AGA CAT CGC ACT GAC TGA GAA C 3′(SEQ ID NO: 22) 56.8 GATA5 Forward 5′ CAC AAG ATG AAT GGC GTC AA 3′(SEQ ID NO: 23) 53.5 Reverse 5′ CTT CCG TGT CTG GAT GCT TT 3′(SEQ ID NO: 24) 55.2 Tbx18 Forward 5′ GGG GAG ACT TGG ATG AGA CA 3′(SEQ ID NO: 25) 56.1 Reverse 5′ AGC AAG AGG AGC CAG ACA AA 3′(SEQ ID NO: 26) 56.5 Tbx5 Forward 5′ ACG TGC TCA GTT TTG CCT CT 3′(SEQ ID NO: 27) 57.2 Reverse 5′ CAG TTT TGT GTT GGC ATT GG 3′(SEQ ID NO: 28) 53.0 Wt1 Forward 5′ CGG GGG TGA ATC TTG TCT AA 3′(SEQ ID NO: 29) 54.2 Reverse 5′ CCT GGA CCA TCC CCT ATT TT 3′(SEQ ID NO: 30) 54.2 Is1-1 Forward 5′ GTA GAG ATG ACG GGC CTC AG 3′(SEQ ID NO: 31) 56.9 Reverse 5′ TTT CCA AGG TGG CTG GTA AC 3′(SEQ ID NO: 32) 55.3 Mef2C Forward 5′ CTG GGA AAC CCC AAC CTA TT 3′(SEQ ID NO: 33) 54.7 Reverse 5′ GCT GCC TGG TGG AAT AAG AA 3′(SEQ ID NO: 34) 55.1Characterization of Cell Surface Epitopes

Pellets of 0.5×10⁶ to 1×10⁶ cells were suspended in 0.5 ml PBS and wereincubated for 30 minutes at 4° C. with monoclonal mouse anti-humanantibodies that were pre-titered for flow cytometry. All antibodiesexcept those against CD133 (Miltenyi Biotech) and CD105 and NG2 (BeckmanCoulter, Miami, Fla.) were purchased from BD Biosciences Pharmingen (SanDiego, Calif.). After labeling, the cells were washed twice with PBS andanalyzed by closed-stream flow cytometry (LSR II, Becton Dickinson,Franklin Lakes, N.J.).

Pulldown (PD) of Growth Factors from EPI CdM

For pulldown (PD) of HGF from EPI CdM, 2 μg of biotinylated human HGFantisera in 100 ul of PBS was added to 1 ml of 30×EPI CdM and incubatedat 4° C. overnight. Separate incubations were performed with 2 μg ofbiotinylated non-specific IgG to produce control 30×EPI CdM. Forsimultaneous PD of 3 growth factors from EPI CdM, 2 μg each ofbiotinylated anti-HGF, anti-VEGF, anti-SDF, or biotinylated IgG (forcontrol) in 100 ul of PBS were added (in combination) to 1 ml of 30×EPICdM and incubated at 4° C. overnight. The following day 0.1 ml of 50%suspension Streptavidin Agarose resin (Pierce, Thermo Scientific) in PBSwas added to each sample and incubated for 2 h at 4° C. with slowrotation. Supernatants were removed after a centrifugation to removeagarose, filtered through 0.22 um syringe filters (Acrodisk) and storedfrozen until use. Biotinylated antisera were obtained from R and DSystems.

Myocardial Infarction

Male mice at 8 weeks of age underwent ischemia-reperfusion myocardialinfarction (MI-IR) surgery (immunodeficient mice: NOD-SCID, NOD-SCIDIL2Rγ^(−/−), and NOD-SCID β2^(−/−), Jackson Labs, Bar Harbor, Me.;immunocompetant mice, C57 bl6/J, Taconic, Hudson, N.Y.). Immunodeficientmice were maintained on a Sulfa-Trim diet and were housed in a standardbarrier facility environment. Any mice with abnormalities in weight,general health, or cardiac health were not included in the study. Micewere also not included in the study if they did not survive the initialmyocardial infarction surgery, did not achieve a successful myocardialinfarction (as determined by blanching observed at time of treatment),or died during treatment application. Following all procedures, micewere given analgesia (buprenorphine, 0.05-0.1 mg/kg i.p.) and monitoredfor signs of distress until termination of the study. All procedureswere done in accordance with the University of Vermont IACUC (protocol08-016).

For the MI-IR surgery, mice were anesthetized using 2-4% IsoFlurane,shaved, weighed, intubated, and then maintained for the duration of theprocedure on a sterile surgical field using a mechanical ventilationsystem (MiniVent, Harvard Apparatus, Holliston, Mass.). Throughout thesurgery and during the recovery period, body temperatures weremaintained with a heated water pad system (Gaymar T-Pump TP-500, GaymarIndustries, Orchard Park, N.Y.). Viewing the chest through a dissectingmicrosope (Stemi 2000-C, Carl Zeiss Microlmaging, Thornwood, N.Y.) adermal incision was made, the underlying fascia were removed, and thethoracic musculature was retracted to expose the left ribcage. Next theintercostal muscles were retracted and the outer (parietal or visceral)pericardium was removed to expose the left coronary artery descending(LCAD). The LCAD was then ligated with 8.0 nylon suture (Henry Schein,Melville, N.Y.) and blanching within the myocardium of the leftventricle was noted. Finally, the intercostals were rejoined using a 6.0nylon suture (Henry Schein), the lungs were reinflated, and overlyingdermis rejoined with a 6.0 nylon suture. All mice were recovered to anambulatory state prior to any subsequent treatment procedure, includingreperfusion.

All surgical attempts and outcomes were extensively recorded, includingthe location of LCAD, suture placement (usually 2.0-3.0 mm from leftatrial apex), area of blanching observed, and any complications noted. Asurgery was considered successful if the mouse survived the initialmyocardial infarction procedure, the suture remained in place for theappropriate time (4 hours), and tissue blanching below the suture wasobserved from initial ligation until reperfusion and/or treatmentadministration. Reperfusion was considered accomplished with a return ofcolor to the previously blanched myocardium. The survival rate for the 4hr MI-I/R surgery was 90%.

Treatment Regimens

Following recovery of animals after initial suture placement, mice wereagain anesthetized, intubated, and the chest opened as describedpreviously at 4 hrs after coronary ligation. Once the intact suture andarea of blanching were confirmed and reperfusion was accomplished,30×EPI CdM (200 uL) warmed to 37° C. was delivered to the entirecardiovascular arterial tree by injecting the solution into the lumen ofthe left ventricle (LV). This method was designed to deliver a maximumamount of EPI CdM to the injured myocardium by employing the naturallyexisting arterial network of the heart, which is supplied by theimmediate portion of the aorta. With a 30.5 gauge needle inserted belowthe great cardiac vein (LV apex) at an angle 45° to the myocardium, 200uL of 30×EPI CdM warmed to 37° C. was slowly injected over a period of 1minute. Control animals received 200 ul of Alpha MEM (vehicle) in thesame manner. All animals were randomized to treatment at the end of thefirst surgery (after ligation). Following treatment with either EPI CdMor vehicle, the needle was removed and the intercostals were rejoinedusing 6.0 chromic gut suture (Ethicon, Johnson and Johnson, Inc.,Livingston, UK), lungs then reinflated, and overlying dermis rejoinedwith 6.0 nylon suture. All mice were then recovered to an ambulatorystate and transferred to the vivarium for the remaining duration of theexperiment. The survival rate for treated immunodeficient mice was:Alpha MEM, 71%; EPI CdM, 75%. The survival rate for treatedimmunocompetent mice was: Alpha MEM, 43%; EPI CdM, 86%.

Echocardiography

Two dimensional, Doppler, and M-Mode echocardiography was performed witha Vevo 770 High-Resolution Imaging System (VisualSonics, Toronto, ON,Canada). Data was recorded from sham-operated mice, control mice withmyocardial infarction, and treated mice with myocardial infarction whileunder isoflurane anesthesia. All left ventricular dimensions in systoleand diastole were measured from M-mode images obtained at themid-papillary muscle level. Echocardiographic data were coded forunbiased measurements and determination of ECHO wall motion scores. ECHOscores were determined from functional assessment of 13 segments using amodel based on the American Society of Echocardiography 17 segmentmodel. Systolic wall motion scores were assigned to 4 quadrants each of3 short axis segments taken at apical, mid papillary, and basal levels,with an additional segment at the apex (13 total). Scores were assignedas: 1=normal, >25% motion; 2=hypokinetic, 10-25% motion; 3=akinetic,<10% motion. Pulmonary arterial Doppler flow velocities and volumes werequantified as in Baumann et al., 2008 Echocardiography. 25: 739-748.

Following ECHO, the mice were killed humanely by exsanguination and thehearts were removed and rinsed in PBS. For creatine kinase assays, leftventricular tissue was dissected away from the atria and the aorta,further separated into anterior left ventricle and posterior leftventricle/septum, and immediately snap frozen by submersion of cryovialsin liquid N₂. The LV tissues were maintained at −80° C. until the day ofthe creatine kinase assay. For histology, the ventricles were dissectedand rinsed in PBS. They were fixed for 2 days in 4% paraformaldehyde inPBS at 4° C. After fixation, the ventricles were cut transversely acrossthe mid portion of the infarct zone, and placed into 70% ethanol priorto paraffin imbedding. Serial sections were cut from each of the twohalves to section the entire heart from apex to base.

Creatine Kinase Assay

The remaining creatine kinase (CK) activity in left ventricular tissueswas assessed to determine the extent of infarction (Zaman et al. 2009Exp Biol Med (Maywood). 234: 246-254). The loss of creatine kinaseactivity directly reflects the loss of viable myocardium aftermyocardial infarction (Kjekshus and Sobel. 1970 Circ Res 27:403-414;Roberts et al. 1975 Circulation 52: 743-754; Shell et al. 1973. J ClinInvest 52: 2579-2590). The percentage of left ventricle with infarctionwas calculated based on observed total left ventricular creatine kinaseactivity (IU/mg protein) in left ventricles of normal hearts withoutinfarction. The percent of myocardial infarction=100×[NL CK-LV CK]/Δ,where NL CK normal left ventricle creatine kinase activity is the amountof CK in tissue from normal left ventricle (IU/mg of soluble protein),left ventricle creatine kinase is total remaining creatine kinaseactivity in the left ventricle after myocardial infarction (IU/mgsoluble protein), and A is the difference between the amount of creatinekinase in normal zones of myocardium and in zones of myocardium withinfarction.

Statistical Analysis.

All values are expressed as mean±SEM unless otherwise indicated.Comparisons of parameters among the three groups were made using one-wayanalysis of variance (ANOVA) followed by Scheffé's multiple comparisontest. Comparisons of parameters between two groups were made by unpairedStudent's t-test. P≦0.05 was considered significant.

The results described in Examples 3-5 were carried out using thefollowing methods and materials.

Epicardial Precursor Cell Conditioned Medium (EPI CdM).

After EMT, passage 3 epicardial precursor cells were seeded and grown inClaycomb expansion medium on 150 cm² dishes (Nunc). When the cellsreached 90% confluence, the plates were washed twice with PBS andserum-free alpha MEM was placed on the cells (20 mls per plate). After48 hours of incubation, the CdM was collected, filtered (0.2 μm PESmembrane, Nalgene MF75, Rochester, N.Y.), and concentrated 30-fold witha Labscale™ TFF diafiltration system with the use of filters with a 5 kDcut-off (Millipore, Bedford, Mass.).

Medium components above 5 kD were concentrated (base medium componentsand salts remained at 1×). One ml vials of CdM were frozen and stored at−80° C. Some of the EPI CdM was kept at 1× (unconcentrated) for ELISAsand cell protection assays with primary human cardiac endothelial cells.ELISAs for human growth factors were performed with commerciallyavailable kits (R and D systems).

Cell Protection Assays with EPI CdM

Primary human aortic and coronary artery endothelial cells werepurchased and cultured in EGM-2MV (Cambrex, Lonza). For cell protectionassays under simulated ischemia, endothelial cells were seeded at 10,000cells/cm² into 24 well plates (Nunc) containing growth medium andallowed to incubate for 2 days under normoxic conditions. Forexperiments, the cells were washed once with PBS and the medium wasswitched to either growth medium, alpha MEM base medium, 1×EPI CdM, or10×EPI CdM. After changing the medium, the cells were then incubated ina dedicated incubator set to 1% oxygen for 24 or 48 hrs. Forneutralization studies, monoclonal antisera against HGF or VEGF wereadded to EPI CdM, incubated for 30 min at RT, and spun down (HGF, H1896;VEGF, V4758; Sigma). For controls, non-specific mouse IgG (Sigma) wasadded to EPI CdM at the same concentration and incubated similarly. Cellviability (metabolism) was determined by MTS assay (CellTiter 96AQueousOne Solution Cell Proliferation Assay, Promega). Cell number wasquantified by dye binding of nucleic acids (CyQuant Assay, MolecularProbes, Invitrogen).

FITC-Alb Extravasation Assay for Vascular Integrity

At 22 hr after MI, reperfusion and treatment (2 hr beforeeuthanization), 200 ul of FITC-conjugated albumin (5 mg/ml in PBS,Sigma) was injected by tail vein. Hearts were removed, fixed in 4%paraformaldehyde in PBS, processed in O.C.T. Compound (Tissue Tek), andserially sectioned from apex to base on a cryostat to 40 micronthickness. TUNEL staining was performed on all sections using acommercially available kit (In Situ Cell Death Detection Kit,tetramethyl rhodamine version, Roche Applied Science).

For each LV section, multiple photomicrographs were obtained at 5×magnification to image the entire LV and were montaged in AdobePhotoshop. Total LV areas and FITC-positive areas were determined fromcomposite, flattened montages with Scion Image Software. LV volumes andFITC-positive volumes were estimated using measurements from 6-7sections that were equi-distant from each other and that spanned theentire zone of infarction. The volumes between sections were estimatedby averaging the section areas for total LV and FITC-positive LV andmultiplying by the distance between the sections (typically 720microns). For TUNEL scoring of FITC-Alb sections, separate images wereobtained outside, at border areas, and inside the FITC-positive area foreach section.

Determination of PTX3 in Blood Serum

Immediately before removing hearts for fixation and sectioning for theFITC-Alb assay, blood was collected by syringe from the left ventricularlumen, allowed to clot, and then centrifuged to collect serum. Due tothe relatively high concentrations of circulating PTX3 in blood ofanimals with MI, serum samples were diluted in buffer prior to ELISA.Murine PTX3 was measured by ELISA according to the manufacturer'sinstructions (R & D Systems).

Other Embodiments

From the foregoing description, it will be apparent that variations andmodifications may be made to the invention described herein to adopt itto various usages and conditions. Such embodiments are also within thescope of the following claims.

The recitation of a listing of elements in any definition of a variableherein includes definitions of that variable as any single element orcombination (or subcombination) of listed elements. The recitation of anembodiment herein includes that embodiment as any single embodiment orin combination with any other embodiments or portions thereof.

All patents and publications mentioned in this specification are hereinincorporated by reference to the same extent as if each independentpatent and publication was specifically and individually indicated to beincorporated by reference.

References

The following documents are cited herein.

-   1. Beltrami, A. P. et al. Adult cardiac stem cells are multipotent    and support myocardial regeneration. Cell 114, 763-776 (2003).-   2. Dawn, B. et al. Cardiac stem cells delivered intravascularly    traverse the vessel barrier, regenerate infarcted myocardium, and    improve cardiac function. Proc. Natl. Acad. Sci. USA. 102, 3766-3771    (2005).-   3. Amado, L. C. et al. Cardiac repair with intramyocardial injection    of allogeneic mesenchymal stem cells after myocardial infarction.    Proc. Natl. Acad. Sci. USA 102, 11474-11479 (2005).-   4. Kawamoto, A. et al. CD34-positive cells exhibit increased potency    and safety for therapeutic neovascularization after myocardial    infarction compared with total mononuclear cells. Circulation 114,    2163-2169 (2006).-   5. Iso, Y. et al. Multipotent human stromal cells improve cardiac    function after myocardial infarction in immunodeficient mice without    long-term engraftment. Biochem. Biophys. Res. Com. 354, 700-706    (2007).-   6. Winter, E. M. et al. Preservation of left ventricular function    and attenuation of remodeling after transplantation of human    epicardium-derived cells into the infarcted mouse heart. Circulation    116, 917-927 (2007).-   7. Smith, R. R. et al. Regenerative potential of    cardiosphere-derived cells expanded from percutaneous endomyocardial    biopsy specimens. Circulation 115, 896-908 (2007).-   8. Gnecchi, M., Zhang, Z., Ni, A., & Dzau, V. J. Paracrine    mechanisms in adult stem cell signaling and therapy. Circ. Res. 103,    1204-1219 (2008). Review.-   9. Gnecchi, M. et al. Paracrine action accounts for marked    protection of ischemic heart by Akt-modified mesenchymal stem cells.    Nat. Med. 11, 367-368 (2005).-   10. Gnecchi, M. et al. Evidence supporting paracrine hypothesis for    Akt-modified mesenchymal stem cell-mediated cardiac protection and    functional improvement. FASEB J. 20, 661-669 (2006).-   11. Lee, R. H. et al. The CD34-like protein PODXL and    alpha6-integrin (CD49f) identify early progenitor MSCs with    increased clonogenicity and migration to infarcted heart in mice.    Blood 113, 816-826 (2009).-   12. Johnston, P. V. et al. Engraftment, differentiation, and    functional benefits of autologous cardiosphere-derived cells in    porcine ischemic cardiomyopathy. Circulation 120, 1075-1083 (2009).-   13. Gittenberger-de Groot, A. C., Vrancken Peeters, M. P.,    Bergwerff, M., Mentink, M. M., & Poelmann, R. E. Epicardial    outgrowth inhibition leads to compensatory mesothelial outflow tract    collar and abnormal cardiac septation and coronary formation. Circ.    Res. 87, 969-971 (2000).-   14. Eralp, I. et al. Coronary artery and orifice development is    associated with proper timing of epicardial outgrowth and correlated    Fas-ligand-associated apoptosis patterns. Circ. Res. 96, 526-534    (2005).-   15. Dettman, R. W., Denetclaw, W. Jr., Ordahl, C. P., & Bristow, J.    Common epicardial origin of coronary vascular smooth muscle,    perivascular fibroblasts, and intermyocardial fibroblasts in the    avian heart. Dev. Biol. 193, 169-181 (1998).-   16. Vrancken Peeters, M. P., Gittenberger-de Groot, A. C.,    Mentink, M. M., & Poelmann, R. E. Smooth muscle cells and    fibroblasts of the coronary arteries derive from    epithelial-mesenchymal transformation of the epicardium. Anat.    Embryol. (Berl). 199, 367-378 (1999).-   17. Pérez-Pomares, J. M. et al. Origin of coronary endothelial cells    from epicardial mesothelium in avian embryos. Int. J. Dev. Biol. 46,    1005-1013 (2002).-   18. Zhou, B. et al. Epicardial progenitors contribute to the    cardiomyocyte lineage in the developing heart. Nature 454, 109-113    (2008).-   19. Cai, C. L. et al. A myocardial lineage derives from Tbx18    epicardial cells. Nature 454, 104-108 (2008).-   20. Eralp, I. et al. Epicardium-derived cells are important for    correct development of the Purkinje fibers in the avian heart. Anat.    Rec. A Discov. Mol. Cell. Evol. Biol. 288, 1272-1280 (2006).-   21. Eid, H. et al. Role of epicardial mesothelial cells in the    modification of phenotype and function of adult rat ventricular    myocytes in primary coculture. Circ. Res. 71, 40-50 (1992).-   22. Chen, T. H. et al. Epicardial induction of fetal cardiomyocyte    proliferation via a retinoic acid-inducible trophic factor. Dev    Biol. 250, 198-207 (2002).-   23. Lepilina, A. et al. A dynamic epicardial injury response    supports progenitor cell activity during zebrafish heart    regeneration. Cell 127, 607-619 (2006).-   24. Zhou, B. et al. Adult mouse epicardium modulates myocardial    injury by secreting paracrine factors. J Clin Invest. 121, 1894-1904    (2011).-   25. Kjekshus, J. K., & Sobel, B. E. Depressed myocardial creatine    phosphokinase activity following experimental myocardial infarction    in rabbit. Circ. Res. 27, 403-414 (1970).-   26. Shell, W. E., Lavelle, J. F., Covell, J. W., & Sobel, B. E.    Early estimation of myocardial damage in conscious dogs and patients    with evolving acute myocardial infarction. J. Clin. Invest. 52,    2579-2590 (1973).-   27. Roberts, R., Henry, P. D., & Sobel, B. E. An improved basis for    enzymatic estimation of infarct size. Circulation 52, 743-754    (1975).-   28 French, C. J., Spees, J. L., Zaman, A. K., Taatjes, D. J., &    Sobel, B. E. The magnitude and temporal dependence of apoptosis    early after myocardial ischemia with or without reperfusion.    FASEB J. 23, 1177-1185 (2009).-   29. Salio, M. et al. Cardioprotective function of the long pentraxin    PTX3 in acute myocardial infarction. Circulation 117, 1055-1064    (2008).-   30. Tarikuz Zaman, A. K. M., French, C. J., Spees, J. L.,    Binbrek, A. S., & Sobel, B. E. Vascular rhexis in mice subjected to    non-sustained myocardial ischemia and its therapeutic implications.    Exp. Biol. Med. (Maywood) 236, 598-603 (2011).-   31. Latini, R. et al. Prognostic significance of the long pentraxin    PTX3 in acute myocardial infarction. Circulation 110, 2349-2354    (2004).-   32. Deuse, T. et al. Hepatocyte growth factor or vascular    endothelial growth factor gene transfer maximizes mesenchymal stem    cell-based myocardial salvage after acute myocardial infarction.    Circulation 120, S247-S254 (2009).-   33. Mangi, A. A. et al. Mesenchymal stem cells modified with Akt    prevent remodeling and restore performance of infarcted hearts. Nat.    Med. 9, 1195-1201 (2003).-   34. Nguyen et al. Improved function and myocardial repair of    infarcted heart by intracoronary injection of mesenchymal stem    cell-derived growth factors. J. Cardiovasc. Trans. Res. 3, 547-558    (2010).-   35. Kloner, R. A., Ganote, C. E., & Jennings, R. B. The “no-reflow”    phenomenon after temporary coronary occlusion in the dog. J Clin    Invest. 54, 1496-1508 (1974).-   36. Reffelmann, T., Hale, S. L., Dow, J. S., & Kloner, R. A.    No-reflow phenomenon persists long-term after ischemia/reperfusion    in the rat and predicts infarct expansion. Circulation 108,    2911-2917 (2003).-   37. Ragosta, M. et al. Microvascular integrity indicates myocellular    viability in patients with recent myocardial infarction. New    insights using myocardial contrast echocardiography. Circulation 89,    2562-2569 (1994).-   38. Ambrosio, G., Weisman, H. F., Mannisi, J. A., & Becker, L. C.    Progressive impairment of regional myocardial perfusion after    initial restoration of postischemic blood flow. Circulation 80,    1846-1861 (1989).

What is claimed is:
 1. A cellular composition comprising an isolatedspheroid epicardial progenitor cell or progeny cell thereof thatexpresses epicardin, GATA 5, WT1, Tbx18, Mef2c, and Tbx5 and is selectedas floating or loosely adherent, wherein the epicardial progenitor cellsare negative for c-kit and CD31, and give rise to a cell of theepicardium.
 2. The composition of claim 1, wherein the cellularcomposition comprises cells that express one or more polypeptidesselected from the group consisting of GATA 4, myocardin, CD105+, CD90+,CD73+, CD44+, CD29+, and Stro-1.
 3. The composition of claim 1, whereinthe cellular composition comprises cells that fail to express detectablelevels or express reduced levels of a polypeptide selected from thegroup consisting of CD34+, CD45+, and vascular pericyte marker.
 4. Theisolated epicardial progenitor cell of claim 1, wherein the cellsecretes HGF, VEGF, SDF-1 alpha, and IGF-1.
 5. The cellular compositionof claim 1, wherein the cellular composition expresses von Willebrandfactor and smooth muscle actin following differentiation.
 6. An isolatedspheroid epicardial progenitor cell that expresses epicardin, GATA 5,WT1, Tbx18, Mef2c, and Tbx5 and is selected as floating or looselyadherent, wherein the epicardial progenitor cells are negative for c-kitand CD31, and give rise to a cell of the epicardium.
 7. The isolatedspheroid epicardial progenitor cell of claim 6 that expresses apolypeptide selected from the group consisting of GATA 4, myocardin,CD105+, CD90+, CD73+, CD44+, CD29+, and Stro-1.
 8. The isolatedepicardial progenitor cell of claim 6, wherein the cell secretes one ormore of HGF, VEGF, SDF-1 alpha, and IGF-1.
 9. The isolated epicardialprogenitor cell of claim 6 that fails to express detectable levels orexpresses reduced levels of a polypeptide selected from the groupconsisting of CD34+, CD45+, and vascular pericyte marker.
 10. Theisolated spheroid epicardial progenitor cell of claim 6, wherein thecell expresses von Willebrand factor and smooth muscle actin followingdifferentiation.
 11. A method for producing a pharmaceutical compositioncomprising cellular factors having cardiac protective activity, themethod comprising: selecting an isolated epicardial progenitor cell ofclaim 6; and isolating one or more cellular factors from the cell,thereby generating a composition that promotes cardiac tissue repair.12. A method for identifying an agent useful for cardiac tissue repairor regeneration, the method comprising: contacting a cardiac cell atrisk of cell death with a composition comprising a secreted cellularfactor isolated from an epicardial progenitor cell of claim 6 selectedfor expression of epicardin, Isl-1, GATA 5, WT1, Tbx18, Mef2c, and Tbx5;detecting an increase in cell survival, growth, or proliferation or adecrease in cell death relative to an untreated control cell; andisolating the agent, thereby identifying an agent useful for cardiactissue repair or regeneration.
 13. An isolated population of thespheroid epicardial progenitor cells, wherein the epicardial progenitorcells express epicardin, GATA 5, WT1, Tbx18, Mef2c, and Tbx5 and isselected as floating or loosely adherent, and are negative for c-kit andCD31, and give rise to a cell of the epicardium.
 14. The isolatedpopulation of epicardial progenitor cells of claim 13, wherein theepicardial progenitor cells express a polypeptide selected from thegroup consisting of GATA 4, myocardin, CD105+, CD90+, CD73+, CD44+,CD29+, and Stro-1.
 15. The isolated population of epicardial progenitorcells of claim 13, wherein the epicardial progenitor cells fail toexpress detectable levels or expresses reduced levels of a polypeptideselected from the group consisting of CD34⁺, CD45, and vascular pericytemarker.
 16. The isolated population of claim 13, wherein the populationexpresses von Willebrand factor and smooth muscle actin followingdifferentiation.
 17. A method of culturing an isolated spheroidepicardial progenitor cell or progeny thereof that expresses epicardin,GATA 5, WT1, Tbx18, Mef2c, and Tbx5, comprising culturing an isolatedepicardial progenitor cell or progeny thereof and selecting from saidculture spheroid cells that are floating or loosely adherent, and arenegative for c-kit and CD31, and give rise to a cell of the epicardium.18. The method of claim 17, wherein the epicardial progenitor cellexpresses von Willebrand factor and smooth muscle actin followingdifferentiation.
 19. A method of isolating an epicardial progenitor cellor progeny thereof that expresses epicardin, GATA 5, WT1, Tbx18, Mef2c,and Tbx5, the method comprising (a) culturing a mixed population ofcells derived from cardiac tissue; and selecting from said cultureloosely adherent aggregates and floating spheroid cells, therebyisolating epicardial progenitor cells that express epicardin, GATA 5,WT1, Tbx18, Mef2c, and Tbx5, and are negative for c-kit and CD31, andgive rise to a cell of the epicardium.
 20. The method of claim 19,wherein the epicardial progenitor cell expresses von Willebrand factorand smooth muscle actin following differentiation.